death." Mr. Steuart was sure that increasing the flash to 100° F. would not increase the price in this country by more than one penny per gallon.

The danger of ordinary petroleum at present was not an imaginary one. Mr. Alfred Spencer gave (from the Registrar-General's Returns) the average number of deaths from lamp explosions as 100 a year in England and Wales, and he believed there were twice as many from upsetting of lamps. That would make a total of 300 deaths per year for England and Wales. Then there was the destruction of property, and the constant fear of accident. Against the proposed change of flash-point, there would be a temporary inconvenience and decreased dividend to the foreign producers of petroleum. This, he was sure, would only be temporary. And what was still a greater objection, an increase in the price of oil to the poor, of perhaps a Fenny per gallon. The oil of the rich would probably be cheapened. The saving of life and property, and the absence of risk and fear, were strong reasons for the proposed alteration.

By the extinction of the Scottish oil trade, they would be at the mercy of foreigners, who would combine to raise the price of oil, and in time of war, with foreign trade impeded, the inconvenience and hardship to the poor would be very great. Yet not even to avoid this would he propose anything of the nature of protection. If the home trade could not compete with foreigners on true terms of equality, it should cease to exist. He would, however, like the trade to get fair play in the competition. He did not think, however, that the Scotch oil manufacture was in danger of extinction at present.

His experiments were more than sufficient in his own opinion to neutralise the report by Abel and Redwood; but he could not expect others to be so easily satisfied. He might be looked on as an interested witness. If so, a committee should be appointed of sufficient weight to satisfy the world. It was ascertainable facts they had to deal with, and mere opinion was nothing. If high flash did not produce extra heat in burning, then the higher the flash, the safer the oil.

He thought it was most important that qualified men oatside the trade should speak and tell them, whether they considered that the flash-point should be raised, and also whether they were sure that by doing so, they were not incurring any other danger. If all were satisfied as to these points already, and passed a resolution to that effect, no doubt it would help greatly to induce the Government to reconsider and re-investigate the matter. He thought 100° was quite safe enough for ordinary lamps in an ordinary state of cleanness. They must not go beyond the practical requirements of the case for fear of raising the price too much. There had been a few bad accidents from overturning lamps with high flash oil, but they must not let these influence them more than justice required. Flour dust in mills was explosive, and coal dust in mines, yet flour and coals were not looked on as dangerous; so neither should high flash oil be looked on with any fear, or burdened with onerous restrictions, because of a few fires produced by unusual circumstances not likely to be repeated.

Mr. J. GRAY said he thought it would be admitted by all who looked at the subject in an unbiassed way, that a clear case had been made out by Mr. Steuart in favour of raising the legal minimum flash-point of burning oil.

He hoped to have had some experiments made in connection with the subject, but his time had been otherwise taken up since the reading of Mr. Steuart's paper. He had observed, however, that in the case of an ordinary Scotch burning oil flashing about 120° F., and working with a small oil container filled exactly half-full (which condition might be taken as a probable average of the lamps in general use), the temperature required to produce an explosive mixture was considerably above the flash point of the oil, whilst, in the case of a sample of American petroleum, flashing at 76° F., the difference between the flash-point and the temperature at which an explosive mixture was formed, under exactly similar conditions, was very much less. The explosive force in the case of the low flash-point oil was slightly greater than in the case of the high flashpoint oil. In his experiments, the explosions were effected

by means of an electric spark, and the force of the explosion was measured by means of a mercury gauge fitted with a registering arrangement. He drew attention to the large quantity of mineral oils used at the present time in heating stoves. He did not remember ever hearing of any accident due to the employment of mineral oils for this purpose, but he had noticed the oil-container in some cases got very hot from radiation. In one instance the temperature of the oil reached 93°, a very dangerous temperature for a low flash oil. In the event of further inquiry into the matter, he thought some information should be obtained on this point. The employment of lamp shades had a decided influence on the heat of the oil container, and consequently on the oil itself. In the case of opal glass shades, especially, there was a large amount of heat reflected on the oil font. He had had occasion to handle lamps for a good many years, privately as well as in business, and he had frequently found the oil in the fonts over 80° F. under ordinary conditions. He had never seen even the semblance of an explosion under these conditions, but then the oil was always from 110° to 120° F. flash-point.

Great stress had already been laid, and rightly too, on that most peculiar, and as yet unexplained anomaly whereby Government legalised oil having a flash-point of 73° F. as safe for the general public, whilst a minimum flash-point of 105 F. was required by the War Office, and 145° F. by the Lighthouse Commissioners for all mineral burning oils supplied to them. That of itself was surely sufficient to demand an impartial inquiry into the question.

Since Mr. Steuart's paper was read, there had been several petroleum accidents reported. A lamp explosion in Ireland caused the death of two girls, a fire in a workhouse in England resulted in the death of two inmates, and an explosion on board a British vessel on the Seine, was accountable for the loss of nine lives. In all, 13 lives within a month. And yet the Home Secretary had written to Mr. Steuart that he was advised that there are not sufficient grounds either of safety or convenience, for an alteration of the existing flashing point for mineral oils."

In Allen's Cominercial Organic Analysis, Vol. II., page 391, under the heading of petroleum, there occurred the sentence," Clearly, the lower the temperature at which an oil flashes,' the more dangerous its transportation, storage, and use must become." Page 400, foot-note 1, it was stated, "B. Redwood to whom the author is indebted for a perusal and revision of the entire article on petroleum products." He argued that as Mr. Redwood had revised this article, he must be held as concurring in it. It would be interesting to know how he reconciled this statement with the views expressed in his joint report, and with his remarks before the Society of Arts.

That a high flash-point tended to increased safety was freely admitted even by those responsible for the manufacture of low flash-point oils. He quoted from an advertisement of an American petroleum in which it was claimed that "its fire-test is so high as to make it the safest lamp oil made from petroleum." The flash-point of this brand he found to be 104° F. Regarding another brand of American petroleum, it claimed that it had "the splendid record of absolute immunity from accident." Mr. Fox, chemist to the Petroleum Association, certified the flash-point to be 116° F. and testified "that this oil possesses the maximum amount of safety to be procured in a petroleum." Mr. Boverton Redwood too, gave this oil a testimonial, in which he said, "possessing in a high degree the various qualities which are desirable in a product of this description." This testimonial bore a date so recent as June 1892. Could Mr. Redwood have changed his mind on this vital question, since he compiled his joint report with Sir F. Abel?

He submitted that it was abundantly proved that a high flash-point secured greater safety, and that 100° F. was the lowest point which could safely be fixed upon as the minimum flash-point. The subject was fully ripe for inquiry. Public interest was aroused in it, and action must be taken in one way or another. He awaited with great interest, the steps which the Section might decide to take with a view to bringing the subject to a satisfactory issue.

Mr. YOUNG, of the Linlithgow Oil Company, did not claim to be an oil expert, but desired to make a few remarks on a

subject of such public interest. In their report Sir Frederick Abel and Mr. Redwood admitted that when the flashing point of oil was even a little above the legal standard, i.e., 73°, vapour would be given off comparatively freely. But they went on to say that oil of a high flash-point evolved a vapour more dangerous than that evolved by a low flash oil. In view of this statement it would be interesting to know what mean point Sir F. Abel and Mr. Redwood would name as that of perfect safety. In connection with the standards fixed by the War Office and by the Lighthouse Commissioners, it was worthy of remark that Sir Frederick Abel himself, being chemist to the War Department and chemical referee to the Government, doubtless gave the advice by which the War Office and lighthouse standards were fixed. Why had Sir F. Abel and Mr. Redwood fixed these standards so high? Americans laid great stress upon the high flash test, and it was a significant fact that all their 66 low grade" oils were sent to this country. The British Government standard admitted of those low grade oils being imported. It was rather unfair that the United Kingdom should be the dumping ground for inferior qualities of American and Russian oil. Mr. Bedford of the Standard Oil Company said that no American would burn low grade oil, and expressed some surprise that the British should be content with oil considered by Americans to be inferior and unsafe. He (the speaker) repudiated insinuations which had been made to the effect that this movement on the part of the Society had for its object a revival of protection in this country. Protection was not desirable, nor could they get it, but the question before them was a practical one which concerned the public safety. He suggested that the Society should appoint a committee, with power to consult two or three chemists of high standing, who should be asked to state whether, in their opinion, the present standard was proper or should be raised. If they said that the present standard was safe, the minds of people would then be at rest. If, upon the committee's advice, Government raised the flash point to 100°, 105°, or 110°, there would be no difficulty in making oil of these standards; it might cost an extra penny per gallon, probably less.

The CHAIRMAN said that while it was most desirable that such a committee should be appointed, and experts consulted, he questioned if the Section had power to grant the necessary funds.

Mr. YOUNG did not anticipate the slightest difficulty in getting the money.

The CHAIRMAN suggested that the money might be raised by the Oil Association, but a committee so subsidised would be liable to be considered somewhat one-sided, and so lose weight. In justice to Sir F. Abel and Mr. Redwood he might remark that he did not think those gentlemen took upon themselves the responsibility of fixing the flash point at 73°. Sir Frederick Abel read a paper in 1881, in which he stated that oil which flashed at the old standard of 100° with the old apparatus, flashed at 73° in the new one. That was how 73° F. was fixed. Tests with the same oil were made by several independent chemists, and 73° F. was accepted by the Scottish Mineral Oil Association. In 1888, before the consultative committee on petroleum legislation, which included four members of the Scottish Mineral Oil Association, Mr. Mann, of Young's Oil Company, Mr. Scott, of the Clippens Oil Company, Mr. Wishart, of the Oakbank Oil Company, and Mr. Young, of Linlithgow, Mr. Mann acknowledged that the Government had been wise in fixing the flashing point of burning oil at 73° F. He (the speaker) certainly thought that 73° F. was too low, but he did not think that Sir Frederick Abel and Mr. Redwood would altogether accept the responsibility for having fixed it.

Professor CRUM BROWN said that he would be sorry if anything went out from that meeting which would appear to reflect upon Sir Frederick Abel. They all knew that Sir Frederick was a perfectly honest and fair man. He was sure that even in the heat of argument none of the speakers suggested anything beyond possible mistake. Their only desire was to secure safety from accident, and

it had occurred to him that help, and possibly even funds, to carry out investigations might be obtained from the fire insurance companies, who were interested in promoting legislation calculated to diminish risk of fire. Referring to the constitution of an investigation committee he deprecated the employment upon it of chemists, and especially of those interested in the manufacture or sale of oil. In his opinion the committee should rather consist of business men who would be guided by competent evidence, including that of experts. Personally, he had never investigated specially the character and composition of burning oils. He had once been present when a lamp was upset; it went out immediately, and no damage was done. In making these remarks his judgment was influenced by no interest in the sale or manufacture of oils, but solely by a desire for public safety.

The CHAIRMAN asked if he would consider an oil of 73° flash too low?

Professor CRUM BROWN replied that as he had never made personal experiments his opinion was valueless, compared with that of people who had made them, but common sense dictated the conclusion that any substance which gave off inflammable vapour at ordinary summer heat, or in warm rooms, was dangerous, and demanded special precautions in its use as an illuminant.

Dr. STEVENSON MACADAM said, that the subject was one of great importance. He had great experience in the testing of paraffin oil. From the first the general understanding had been that any oil which, under ordinary circumstances of burning in a common lamp, gave off inflammable vapour under 100° F. was unsafe for domestic use. It was upon that understanding that the first testing apparatus-the open one-had been employed. But when by and bye the close-testing apparatus came into use it was found that an oil, which had been considered safe because it had not flashed below 100° in the open tester, evolved inflammable vapour as low as 80° in the close tester, and was therefore dangerous. When the testing apparatus got still further improved, it was discovered that this same oil would give off inflammable vapour at 73°. So that an oil, which was previously supposed not to flash below 100°, was now found to flash at 73°. Government had made the mistake of assuming that having fixed the standard at 100° they might, in the light of more recent experiment, safely bring down the standard to 73°. They should have adhered to the original standard of 100°, no matter what the testing apparatus was. If they had done so the quality of paraffin burning oils would have been improved, until the country would have been supplied with really safe oils, with a flash point of something like 120° F. in the old open apparatus. He did not attribute the mistake to any bias on the part of any experimenter. It seemed rather that by an error of judgment the standard had been lowered to suit the dangerous oil, instead of the dangerous oil being refined to the safe standard. He was confident that 73° was not a safe flash point for lamp-oil. A lamp which, while clean, might burn a 73° oil with safety would, when the free current of air was obstructed by dirt, get heated as to its fittings, with the result that the temperature of the oil would rise to 80° or more. They all knew also that inferior cheap lamps were so constructed that great heat was communicated to the fittings, and thence to the oil. The question was one not of the safety of oil when burning in the best lamps, but when burning in the lowest class of lamp. As to the very high flash point required for mineral oils used in lighthouses, he might state that the Northern Lighthouse Commissioners were the first to introduce paraffin oil into the lighthouses of the United Kingdom. He along with others conducted the experiments, which resulted in the recommendation that for lighthouse illumination, an oil ought to be used which, whilst giving a good white light, had the highest flash point obtainable in a free burning mineral oil. In conequence of that recommendation the standard had always been from 130° to 140°, or even higher. In lighthouse lamps the highest temperature that the oil attained in any part of the lamp and connections was about 86° F., so that it was quite impossible to use anything like 73° oil

with safety. Oils could now be obtained of much better quality and much more evenly run than they were 20 years ago, and since they could now get better and more evenly run oils, not a mixture of various degrees of gravity and firing point, but of more uniform quality throughout, there was all the more reason to insist upon the original standard of safety, viz., that in the United Kingdom a safe burning oil for ordinary domestic and trade purposes should be one with a flash point not under 100° F. in any recognised testing apparatus,

Dr. AITKEN commended Mr. Steuart's paper as drawing attention to a very important matter, upon which it was evident that Mr. Steuart felt very keenly. But from what he knew of Mr. Steuart, he was perfectly sure that he was actuated by purely humanitarian feeling and not by any self-interested desire to relieve the presently depressed oil trade of Scotland by directing public attention to the superior safety of Scotch over imported oils. He quite agreed with the main drift of the paper, and the general conclusions arrived at, viz., that there was danger in the use of oils of low flash-point. It was evidently the original intention to prohibit the sale of oil flashing below 100°. But in the light of more perfect means of testing the flash-point ought to have been raised, because the conditions under which an explosion might take place in a paraffin lamp, were just the conditions established in the improved apparatus. He hoped the suggestion as to the committee of enquiry would be carried out; not an expert committee entirely, but one which would take the advice of experts. It was a very peculiar thing that in this country, there was in use oil of a flash-point lower than the standard in those countries where low flashing oils were produced.

Mr. J. FALCONER KING said that his opinion that the flashing point of oils was too low, was probably shared by most chemists who had considered the subject. Why the reduction was from 100° to 73° it was difficult to comprehend. The invention of more accurate means of ascertaining flash-point, was no reason for lowering the legal limit of safe temperature below 100°. Several reasons might indeed be stated for raising it. The chief of these was the public safety, but beyond that it was important that, by immunity from accidents in its use, the popularity of paraffin oil as an illuminant should be increased. He would be pleased if, by a resolution of the meeting, or in any other way, something could be done towards putting the matter right.

mean

Mr. W. IVISON MACADAM said they would naturally expect that the flash-point of all oils, to be safe in this country, would be fixed at a point somewhat higher than summer heat. Last summer the temperature one morning stood at 102°. A flash-point of even 100° would obviously not cover that temperature. Therefore it was an argument for a flash-point of at least 110° or 120°. An American oil which he had tested flashed at 69° F. That was the lowest flash he had met with, but he had had samples at 78° or 79°, and these on a day of ordinary summer heat would certainly be most dangerous. He was glad to know that Mr. Redwood agreed that a higher flash-point did not increased temperature in burning. Mr. Steuart's experiments, as well as some made by himself, proved that point. At first sight it appeared that glass lamps were safer than lamps made of metal, because metal conducted heat more readily than glass. This was true to some extent where the wick fittings were of metal, and where the heat of the flame was practically conducted down through the centre; but a glance at the reports of Sir Frederick Abel and Colonel Majendie showed that in all the accidents investigated by them, 23 were in glass apparatus, and four only in metal. He had tried experiments with both metals and glass fittings, and did not find his first conclusion hold good. He did not recollect Mr. Steuart's conclusions on the point, but his impression was that Mr. Steuart rather advocated the adoption of metal than glass.

Mr. STEUART said that on the contrary he advocated glass rather than metal. The metal lamp he used gave an unusually high temperature, 10° higher than the glass lamp.

Mr. IVISON MACADAM continuing said that-The fact remained that of the accidents, 23 were in glass, and four only in metal. He had not the least doubt that the best lamp for ordinary purposes was a fountain lamp, and yet in that kind of lamp, of the best construction, filled with 145° flashing oil and starting with a temperature at 54°, he had found that in 4 hours the oil in the burner had risen to 82°, and the oil in the fountain to 76°. A certain temperature was necessary for the burning of this oil. A flat 1 inch wick gave only 12 candle-power, and 22 lb. of sperm value of oil, while an Argand burner which conserved the heat, and with only 1 inch wick, gave 18.83 candles, and 27.2 of sperm. Other experiments showed that at high temperatures certain oils actually decreased in illuminating power. Dr. S. Macadam knew of one instance in a lighthouse where an extra series of reflectors, by increasing the temperature so diminished the light power that the reflectors had to be removed. He (the speaker) experi. mented with shaded lamps and found that the temperature below the shade frequently rose to 86°; the oil used was a lighthouse oil of 145° flash-point. In oil stoves, the front temperature was frequently over 84°. The flash-point should not have been lowered below 100°. A strong corroboration of that view was to be found in the report by Sir Frederick Abel and Mr. Redwood to the Secretary of State for the Home Department, in which a number of lamp accidents were summarised. (Paragraph 33, page 8.) In one case the oil flashed at 73°, in one at 74°, one at 77°, one at 78°, two at 79°, one at 82, one at 83°, one at 84°, one at 86°, one at 88°, and one at 110°. Notwithstanding that information the Government still retained the low flashing point of 73°. The Society ought to memorialise the Government to increase the flash-point and so increase safety.

Mr. J. STUART THOMSON, thought that one point ought to be made clear. Prior to the introduction of the Petroleum Act of 1879, the Scottish Mineral Oil Association, along with other interested parties, were asked to experiment with the new close test apparatus introduced by Sir Frederick Abel for the purpose of determining what flash temperature in the new apparatus was equivalent to the flash temperature of 100° F. in the open test. The equivalent was ultimately fixed at 73° F., that being the average of a number of experiments made by different operators. Several attempts had been made by the Scottish oil companies to get the minimum flash-peint raised, but the opposing interests had in every case been too strong to allow of their proposals being carried through Parliament. So firmly, however, did the Scottish oil companies believe in the wisdom of their proposai, that they had voluntarily adopted 100° F. close test as their own minimum standard of safety, and it was to this that the immunity of Scottish oil from explosion and accident was solely to be attributed. The proposal to nominate a committee to take evidence and lay the matter before the proper anthorities, was a satisfactory movement on the part of the Society.

Mr. IRVINE, alluding to lamps in which the air supply is fed to the wick through the centre of the oil vessel, thought that it would be interesting to know whether in lamps so constructed the temperature in the oil reservoir was maintained at a lower point, than in lamps where the air was drawn to the wick from the outside.

Professor CRUM BROWN remarked that, in the case of oils which could not be supposed to be homogeneous, Mr. Steuart's table showed that, after burning for a long time, the residue of oil left in the vessel had practically the same specific gravity and flash point as the original oil put in, so that the oil which would be fractionated in a retort, was apparently not fractionated by the wick, and and although evidently a mixture it burned as though homogeneous.

Dr. STEVENSON MACADAM moved the following resolution: "That this meeting is of opinion that further investigation "should be made into the matter of the proper standard of "safety for mineral oils, and that it be remitted to the "committee of the Section to consider the whole subject

"and bring up a report at the next meeting of the Section "indicating their views with regard to the whole matter." Professor Crum Brown seconded the motion, which was adopted unanimously.

Mr. STEUART referring to Mr. Ivison Macadam's remarks as to the comparative safety of metal and glass lamps, said that in order to be of any use the statistics relied upon must take into account the comparative numbers of glass and metal lamps in use in London. As that was not known the numbers quoted by Mr. Macadam offered no reliable data for the conclusion arrived at by that gentleman. Referring to Professor Crum Brown's remarks as to the non-fractionation of the oil by the wick, he (the speaker) accounted for that by the fact that in his experiments the lamp was filled only once. In practice fresh oil would be added to accumulated residues in the lamp, and thus the oil in the font would become heavier. This cumulative effect was not shown by his experiments.

With regard to certain portions of his paper he did not well know what to say. Had he calculated upon its arousing so much interest he would have written some portions with greater reserve and under greater restraint than he had done. He confessed that he had discussed the report of Sir F. Abel and Mr. Redwood under some feeling of indignation and under a strong sense of the duty which lay on him to prove that the report was wrong. The matter was not one of mere rival trades, it was ripe for being taken up in the interests of the public. For he felt that so long as that report was recognised as true scientific teaching, it was a report full of danger and responsible for the annual loss of hundreds of lives. It was doubtless possible to discuss the scientific question without making direct personal reference to the report or its authors, but the matter could not be discussed without passing judgment indirectly on its authors. He had preferred to be rather direct. If this had been an error of judgment on his part he hoped that it would not deter others from supporting a good cause.

Dr. STEVENSON MACADAM thought there was one fact which the investigation committee should take into consideration. It had been shown that oil which gave off inflammable vapour at 73° in this country, gave a flash point of 66° in India. The same result could be obtained in Britain by experimenting in rooms heated to tropical temperature.

The CHAIRMAN said that the German Government fixed the flash point at 72° F., and after the British Government legalised 73° F. and after Sir Frederick Abel read his paper and drew up his report in conjunction with Mr. Redwood. He thought it strange that a nation who usuully investigated scientific matters with great thoroughness should fix the flash point for burning oil at 72°.

Dr. STEVENSON MACADAM believed that the Germans adopted the general principle of Sir Frederick Abel's apparatus, but had so improved the mode of heating, that the oil which flashed in Sir Frederick Abel's apparatus at 73° flashed in their improved apparatus considerably below 73°.

The CHAIRMAN asked Dr. Macadam if he did not think a temperature of 72° too low for national safety?

DR. STEVENSON MACADAM thought so. The fact that such a temperature had been fixed in Germany was due to the delicacy of the testing apparatus.

The CHAIRMAN said the experiments that Mr. Ivison Macadam had made showing that shades on lamps caused a rise in temperature to 86°, appeared to him to be valuable; for in ball rooms, where lamps with shades were so very much employed, the heating of a lamp even 10° or 15° F., when filled with 73° F. flash oil, might be very disastrous, as the air was often over 73° F. to begin with.

A statement had been made at the last meeting, to the effect that oils should be labelled. Government should certainly force the vendors to label oils in the way that other chemicals were distinguished. If the barrels were different colours for different flash points people would know what they were buying, and they would willingly pay a little extra money for an oil which they knew to be perfectly

safe. People had wondered why it was the Government stipulated for 105° for the Army Stores, and 145° for the lighthouses. He thought that the 105° oil was intended for use in India or in other hot climates. It appeared to him that as petroleum tank steamers carried low flashing oils, it was a source of danger to these ships and crews. The Government should put restrictions on such boats, and make their owners take precautions.

If the course was taken which had been suggested moved by Dr. Stevenson Macadam, and seconded by Professor Crum Brown, he was sure that a practical issue would come of the discussion, which would be of national importance.

Mr. IVISON MACADAM said he thought it right to mention that the flash point for India was really 73°, and that the 105° flash point oil was intended for use in Aldershot

XI.-Electro-Chemistry and Electro-Metallurgy
XII.-Fats, Oils, and Soap Manufacture.....

XIII.-Paints, Pigments, Varnishes, Resins, India-
Rubber, &c.

XIV.-Tanning, Leather, Glue, and Size
XV.-Manures, &c.

XVI.-Sugar, Starch, Gum, &c. ..................................
XVII.-Brewing, Wines, Spirits, &c..

XVIII.-Chemistry of Foods, Sanitary Chemistry, and Disinfectants.

XIX.-Paper, Fasteboard, &c......

...........

XX.-Fine Chemicals, Alkaloids, Essences, and Extracts XXI.--Photographic Materials and Processes XXII.-Explosives, Matches, &c....... XXIII.-Analytical Chemistry

I.—GENERAL PLANT, APPARATUS, AND MACHINERY.

The Purification of the Feed-Water for Boilers. H. Schreib. Zeits. f. ang. Chem. 1892, 514-517. THE author draws the following conclusions from his experiments :-(1.) There is no method of purification

Any of these specifications may be obtained by post by remitting Sd.-the price now fixed for all specifications, postage included-to Sir Henry Reader Lack, Comptroller of the Patent Office, Southampton Buildings, Chancery Lane, London, W.c.

that can be regarded as the best; local conditions must determine the method to be adopted. (2.) As a matter of principle the removal of bicarbonates by heating, and of sulphates by means of sodium carbonate is better than the employment of caustic soda, but for practical reasons the use of the latter is often preferable. (3.) No prejudicial results on the boiler attend the use of caustic soda.-C. A. K.

Smoke Prevention. Report of the Special Committee of the St. Louis Engineering Club, U.S.A. Journal of the Association of Engineering Societies, Chicago, 1892, 291; Proc. Inst. Civil Eng. 1892—3, 111, (1) 42—46. THE authors of this report having been charged with the duty of investigating the coal-smoke problem, while making such recommendations as may tend to abate the evil prevailing to a very serious extent in the city of St. Louis, have given careful consideration to a number of general questions relating to the use of fuels which are everywhere applicable. Large coal-users are, as a rule, disappointed with the results they obtain with such smoke-preventing inventions as have hitherto been devised. These inventions are in some cases unsuccessful because of an entire misconception of the principles involved in the combustion of bituminous coal, and in others because of a want of appreciation of the conditions which fix the limitations of successful application; and, lastly, the general public, when inveighing against the want of skill of manufacturers, engineers, and men of science, is too ready to assume that a smoking chimney necessarily represents wasteful combustion of fuel. It seems, then, that the whole community must be educated to a more intelligent under standing of the problem before a satisfactory solution can be successfully brought about.

Examining the principles upon which combustion depends, and the conditions under which smoke is produced or can be prevented, it is pointed out that although by the application of heat the organic matter in coal is decomposed, and gaseous carbon and hydrogen given off, yet the heat may be insufficient to effect a chemical combination between those gases and the oxygen of the air, in which case further heat is not developed, but, on the contrary, absorbed. Again, when the hydrocarbon vapours are decomposed, carbonic acid and water (CO2 + H2O) may result from the complete combustion of some portion of them, while another portion has some of the carbon separated and set free, leaving a light hydrocarbon gas (C2H1 = C + CH1). It is this separated carbon, in an incandescent state, which in the main causes the luminosity of the flame when a heavy hydrocarbon is burnt, and it is this same separated carbon which makes the visible smoke during the combustion of bituminous coal. For the rapid combustion of this separated carbon, not only is a strong oxidising action necessary, but a very high temperature as well, probably not less than 2,000° F. If this high temperature is not supplied in the fireplace, where the gases are generated and the carbon separated, the latter will be carried along by the rapid draught, and pass out unchanged as visible smoke; and, under the usual conditions of coal-combustion, it is impossible to obtain such a temperature at once, because the coal is thrown into the fireplace in cold heaps, and generally in excessive quantities. Its moisture and combined water (together amounting to from 10 to 20 per cent. of the whole weight of the coal) have first to be volatilised, and while their vapour, mixed with a great volume of cold air, is passing off, a large quantity of the produced heat is absorbed.

Not one of the innumerable devices so far brought forward for the prevention of smoke is capable, in its present form and application, of fully meeting and satisfying all the requirements for success. The more important types are classified under the following seven heads :A. Steam jets. B. Firebrick arches, or checker work. C. Hollow walls for pre-heating air. D. Coking arches or chambers. E. Double combustion, F. Downward-draught furnaces. G. Automatic stokers.

A. The object of the steam-jet is to force air into the fireplace, either directly or after being heated, in sufficient quantity above the fuel-bed for the combustion of all combustible material, and to effect such a thorough mingling of the air, gases and carbon that combustion will take place readily, and not far beyond the fireplace. The steam-jet system can undoubtedly be made to yield satisfactory results where the demand upon the boiler is comparatively light and does not vary much; but with variation in the demands upon the boiler, the jets require corresponding adjustment, and such a system is therefore largely dependent upon the skill and care of the fireman. When the nozzles are not very carefully adjusted, they are apt to cause a blow-pipe action upon the boiler-shell or grate-bars, which results in a rapid burning of the metal, especially from the strong oxidising action of the decomposing steam.

B. Firebrick arches are usually placed near the rear end of the fireplace, or over the bridge wall. They cause the smoke, gases, and air to pass through a constricted passage close to the fuel-bed, and serve not only to reflect the heat from it, but as a strong accumulator of heat, which tends to keep the heat up to a more uniformly high temperature. The checker-work is intended to produce the same result in a different way by dividing the general volume of smoke and gases into a number of small currents. With careful firing both these appliances can be made to produce good results, but only to a limited extent; and another and more serious objection is their want of durability and the consequent high cost of repairs and frequent interference with regular operations.

C.-A number of patents have been taken out based upon the system of providing hollow walls for pre-heating air, but the committee considers that they all fall short of the requirements.

D. and E.-The systems classed under the heads of coking arches or chambers, and double-combustion, are also shown to be objectionable.

F.-Downward-draught furnaces consist essentially of a fireplace with the back closed, so that the smoke and gases can only pass away downwards through the fire-bed. This causes such intense heat upon the grate that instead of ordinary bars water-tubes have to be used, and these are so connected with the boiler-shell as to form a part of the water-circulating system, and supply so much additional heating surface. As they require to be at a greater distance apart than ordinary grate-bars, an auxiliary grate of ordinary type is sometimes set some distance below, into which the incandescent fuel falls from above, and through this all the air is delivered for completing the combustion of the gases issuing below the upper grate. Such a system is well adapted to insure a good smoke record, and it has the advantage also of being readily attached to a variety of boilers; but it is liable to defects in construction, while the water-tubes of the grate and the connecting pipes are subjected to unusual strains at the joints, and the latter are not altogether reliable. The system has, however, so many valuable features that it gives great promise for the future, and is well worth the attention and study required to secure the needed improvements.

G.-Automatic stokers are intended to secure regular and uniform feeding of coal to the fireplace by mechanical action, in place of the irregular and unreliable service of the ordinary fireman. The mechanical action may be applied in the form of screw or hopper feeders to fixed inclined grates, or to moveable inclined or step grates. They require the coal to be properly sized as nuts or peas, and under favourable conditions are capable of giving good results, but their limitations are such that they cannot be regarded as applicable to any important extent.

It has been found in practice that, as a rule, all these devices for the prevention of smoke occasion a loss in the heating-power of the fuel. Experiments made at the New York Navy Yard with four different types of nozzles showed that the loss of steam, when steam-jet boilers were employed, was as follows::