oxidise and precipitate the dye. If, however, the wool was not merely dipped in the solution but boiled in it for some time, then the chromic acid would be more or less reduced by the substance of the wool itself, and a proper mordanting of the fibre resulted. The effect of washing the mordanted fibre was to remove chromic acid, and, when logwood was used as the dye, to produce a slightly brighter and bluer, but not quite so full a black. Chrome alum had been experimented with as a mordant by the authors, with results that would be described in a future paper. A knowledge of the process of the chrome tanning of leather would hardly avail to explain what took place in the case of wool, since the operation was carried out in the cold with leather, but at a boiling temperature in the case

of wool.

burning oils flashing at from 73° F. to 86° F. Abel-test, are constantly imported and sold, bearing brands of from 120° F. to 150° F., and thereby the public are misled.

5. All burning oil imported into this country should have the Abel test plainly branded on the cask.

6. Many fatal accidents have occurred from the use of this inflammable oil, and as a measure of precaution socalled " 'safety lamps," constructed of metal, have been recommended. Unless the oil itself is safe, a new source of danger is introduced by "safety lamps."

Your Committee have unanimously adopted the above report, and have now the honour to lay it before you.

It was thereupon resolved unanimously: That this meeting of the Glasgow and Scottish Section of the Society of Chemical Industry hereby approves and adopts the above report of the Committee on the flash-point of mineral oil."

ON THE ACTION OF CAUSTIC POTASH AND CAUSTIC SODA ON PURE GOLD AND SILVER.

BY THE LATE W. DITTMAR, LL.D., F.R.S., AND DAVID

PRENTICE.

INTRODUCTORY.

Dr. G. G. HENDERSON, who read the paper, said that this investigation had been instituted by the late Professor Dittmar, and was in progress at the time of his death. It had been completed by Mr. Prentice, and the results attained, he thought, were of sufficient interest—if not entirely novel— to lay before the section.

PART I.--Action of Caustic Potash and Caustic Soda on pure Gold.

The object of the following experiments was to show how far caustic potash and caustic soda could be dehydrated without acting on pure gold and silver, and how far they acted on those metals when fully dehydrated.

For this purpose a pure gold crucible and a pure silver one were obtained of the shape shown in the figure. Each

Meeting held in the Societies' Rooms, 207, Bath Street, Glasgow, on Tuesday, February 7th, 1893.

MR. CHAS. A. FAWSITT IN THE CHAIR.

THE FLASH-POINT AND HEAT OF BURNING OF MINERAL OILS.

(This Journal 1892, 885-893; and 1893, 20—26). REPORT OF COMMITTEE.

IN pursuance of a resolution passed at the meeting held in Edinburgh on December 6th last, your Committee appointed the following sub-committee to investigate and report upon the present legal flash-point of mineral oil:-The chairman, Mr. C. A. Fawsitt), Mr. G. Beilby, Mr. John S. McArthur, Prof. Edmund J. Mills, Mr. Edward C. C. Stanford and Mr. Daniel R. Steuart.

At a meeting of Committee held this day the sub-committee submitted the following report:

Your sub-committee is of opinion that:

1. The present legal flash-point (i.e., 73° F.) for mineral burning oil is too low, and therefore, under ordinary circumstances, dangerous.

2. The Government Abel-test is perfectly satisfactory for determining the lowest temperature at which inflammable vapours are evolved.

3. 100° F. by this test should be the minimum legal

standard.

1. The Government Abel-test is not invariably employed to determine the flash-point, as is evidenced by the fact, that

was provided with a close-fitting lid, with a perforation in the centre into which a platinum tube was inserted when it was desired to fuse in an atmosphere of hydrogen or nitrogen.

The caustic potash used in all the following fusions was obtained from Merck, and being in lumps was fused in a silver basin and cast into sticks.

It was then tested for iron, alumina, silver (which might have been dissolved off the basin), chlorine, and sulphuric acid, the result showing entire absence of iron, silver, and sulphuric acid, but very small traces, in either case, of chlorine and alumina, which however, were scarcely visible. The caustic soda used in all the fusions was also tested, but was found to be pure.

Carbonic acid was of course tested for, and was found to be present in both cases.

The KO and CO, in each fusion of caustic potash were estimated, and for the determination of the KO by titration a standard solution of sulphuric acid was made up, as well as a (CO-free) solution of caustic potash, the acid being standardised against the alkali. To serve as a check on the results obtained by titration, the KO was also determined gravimetrically by the sulphuric acid method, which will be detailed further on.

The CO was determined in the usual way by the direct method.

The Na O and CO, in each fusion of caustic soda were estimated in the same way as above, with the difference that the Na was not determined gravimetrically, but only by titration.

As it was sometimes desired to fuse in an atmosphere of hydrogen, and to drive out the hydrogen by means of nitrogen to prevent explosions, the two gases were prepared and purified in the following way :

The hydrogen was obtained by acting on zinc with sulphuric acid, and the nitrogen by taking a large tubulated bottle (about 10 litres capacity) and dissolving 12 grms. pyrogallol and 60 grms. caustic soda in water in the bottom of the bottle. This was shaken up for about half an hour (the bottle having communication with another filled with water) and allowed to stand 24 hours, and was then ready for use. The hydrogen, after being evolved from the Kipp, was first passed through a tower containing pumice soaked in mercuric chloride solution to free it from arsenic, then through vitriol, and lastly through a stoppered U-tube charged with freshly-fused caustic potash, and from it into

The nitrogen was first passed through vitriol and then through the same U-tube of caustic potash as above, the two apparatus being connected by means of a three-way stop-cock, by means of which it was easy to substitute a current of nitrogen for one of hydrogen.

Method of Weighing the Caustic Potash and Caustic Soda for the Analysis.-The substance was first put into a small glass tube (A), sealed up at one end, and with a small handle (B), which was simply a piece of glass sealed

on at that end; this was put inside two other tubes, C and D, fitting closely into one another, and each being sealed ap at one end. The substance was of course by this means prevented from taking up moisture from the air. The whole was carefully weighed, the tubes were opened, the small tube taken out by the handle, and the substance emptied into the flask in which the analysis had to be done. The tubes were again put together and weighed, the difference giving weight of substance used.

Method of Determination of K2O and Na.O by Titration. The sulphuric acid used in all the titrations was standardised by the carbonate of soda method, the specific gravity having been previously taken.

The substance, after being weighed in the way described, was dissolved in water in a conical flask, and three drops of a 2 per cent. solution of aurine were added to act as an indicator. A 100 cc. weighing burette was now filled with the standard acid and a 50 cc. measuring burette was filled with the alkali. The burette containing the acid was weighed, and a quantity of acid was run into the flask until the liquid was acid. The red colour was again brought back by addition of alkali (no more being added than was uecestary to make the liquid alkaline); from two to three drops of acid served to make the liquid again acid, and it was then boiled vigorously to expel the CO. After boiling for a short time the red colour was brought back by addition of alkali; the acid burette was weighed and the other read. This operation was repeated once afterwards, two readings being taken in every titration.

it. The bottom of the crucible was now immersed in cold water and the substance dissolved in the smallest possible quantity of water; a slight excess of 60 per cent. H2SO was also added, and the whole was evaporated to dryness by heating from above and very gently from below. The crucible was then heated strongly over a bunsen and weighed.

Method of Determination of Carbonic Acid.-The substance (from 0.5 to 1 grm.) was weighed out and put into a 500 cc. flask with about 50 cc. of water. Immediately above the flask was an inverted condenser, then following this was the drying apparatus, which consisted of (1) a stoppered U-tube charged with fused CaCl, and (2) another stoppered U-tube charged with vitriol and pumice, enough vitriol being put in the bend of the second U-tube to show the rate at which the gas passed through it. The CO, was caught by two stoppered U-tubes, the first containing fresh soda-lime and the second newly-fused caustic potash; a protection tube of CaCl, and soda-lime completed the apparatus. 20 per cent. sulphuric acid was added to evolve the CO2, and the liquid was boiled gently while from 3 to 4 litres of (CO-free) air were passed through the apparatus to drive all the CO, into the collecting tubes.

Notes.-(1.) In all the fusions a hydrogen flame was used instead of a gas flame.

(2.) In all the fusions done "in air" the lid of the crucible was kept on, the perforation in the centre serving as an escape for the vapour of water.

Fusions of Caustic Potash in Gold Crucible.-In the table below (Table I.) are given the results obtained on fusing caustic potash in the gold crucible.

Experiment I.-The potash was fused for five minutes in air, then cast into a small steel mould, and quickly sealed up in clean, dry, glass tubes. When required for analysis the tube was opened with a file, and the substance put into a stoppered tube, which was kept under a good desiccator till it had to be weighed. When the substance was put into the stoppered tube all the weighings were done at

once.

Experiment II. was carried out in the same way as the preceding one, but the fusion was continued for 10 minutes.

Experiment III.-After weighing the potash put into the crucible, the platinum tube was inserted into the perforation in the lid, and hydrogen was passed into the crucible for about 10 or 15 minutes so as to expel all the air. The potash was then fused in the current of hydrogen by heating from below with a hydrogen flame. After five minutes the three-way stop-cock was turned, and nitrogen was passed for five minutes longer. This was done after all the fusions in hydrogen described below.

Experiment IV. was carried out in the same way as Experiment III., but laster longer, viz., 10 minutes in hydrogen and 5 minutes in nitrogen.

Experiment V. was carried out precisely as above, but the current of hydrogen was continued for 25 minutes and the nitrogen for 5 minutes.

The caustic potash used in the experiments was analysed, the KO being estimated by titration, and the CO, by the direct method, with the following results:-K ̧0 (1) 63·30 per cent., (2) 63 49 per cent., mean 63 39 per cent.; CO2 (1) 1·08 per cent., (2) 119 per cent., mean 113 per cent. Fusions of Caustic Soda in Gold Crucible.--Table II., below, gives the results obtained on fusing caustic soda in the gold crucible.

The experiments were done in the same way as with caustic potash. It only remains to note that in Experiment II. the crucible, by some unaccountable means,

E

Fusions of Caustic Soda in Silver Crucible.—In the table below (Table IV.) are given the results obtained on fusing caustic soda in the silver crucible. The experiments were carried out in precisely the same way as those done with caustic potash, and for the same periods of time, viz., No. I., five minutes in hydrogen and five minutes in nitrogen; No. II., 10 minutes in hydrogen and five minutes in uitrogen; Nos. III. and IV., five and 10 minutes respectively in air.

Conclusions.

From the figures given above it is seen that the dehydration of both caustic potash and caustic soda is practically complete after about 10 minutes' fusion, whether the fusion is conducted in hydrogen or in air. The action of fused potash on gold is very slight in a current of hydrogen, even after 30 minutes' fusion, and much greater in air, though still comparatively trifling. Fused caustic soda, on the other hand, appears not to attack gold, either in air or hydrogen-at least, within the duration of the experiments. On silver, as is to be expected, the action of the fused alkalis is easily perceptible, and of course is greatest in presence of air; potash, again, is much more active than soda.

DISCUSSION.

The CHAIRMAN, after thanking Dr. Henderson for having brought the results of this investigation under the notice of the Section, said that when fusing large quantities of caustic soda in silver basins he had noticed that the basins were much attacked. He had attributed this action to the presence of manganate of soda. He asked Dr. Henderson if he could explain the precise cause of the corrosion and why it was so much intensified in presence of air.

PROFESSOR MILLS asked for particulars regarding the colours of the gold and silver after the fusion of the alkalis in the crucibles.

Dr. HENDERSON, in reply, said he was unable to give a definite answer to the Chairman's question, but he thought the action on both gold and silver was one of oxidation. So far as he was aware no record had been kept which would assist him in answering Professor Mills question, but he was under the impression that there was a purple tarnish on the gold crucible, which was easily removed by burning. In the case of silver the action was more a corrosion of the surface.

or run.

PORTLAND cement is mixed with sufficient water to form a stiff paste, so that when applied to a wall it will not fall off This cement may be used for manhole-lids with excellent results. It is applied to the carefully-cleaned surfaces in a layer of from 5 to 8 mm. in thickness. As soon as the cement is applied the lid is carefully put upon it and slowly tightened until the thickness of the layer is reduced to from 3 to 4 mm.. After an interval of several hours the cement begins to set, and now the nuts on the lid are firmly screwed down. During the next eight hours the joint is kept slightly moist so as to prevent haircracks. A manhole packed in this manner never becomes loose. In a similar manner flange-joints on water-, steam-, or airpipes may be tightened by means of cement; such joints, if carefully prepared, prove exceedingly durable, and are much cheaper than india-rubber or asbestos packings.-C. O. W.

Evaporating Apparatus used in the Chemical Industries. J. Dannien. Zeits. ang. Chem. 1892, 479-483. AFTER drawing attention to the fact that the latent heat of steam, amounting to about 85 per cent. of the total heat expended, is still generally lost, the author deals with the forms of apparatus for conducting artificial evaporation in the different branches of the chemical industries.

I. Pans fired from below.-Pans with flat bottoms are still in use in salt-, vitriol-, and alkali-works. Their use is accompanied by high cost of repairs and expensive labour, if salts are deposited. Boat pans and caustic pots are wasteful as regards fuel. Wolf pans with saddle-shaped bottoms, and triple-flued pans such as are now in use at Stassfurt, prevent the burning-on of the precipitated salts; these collect in the cold parts of the

Any of these specifications may be obtained by post by remitting 8d.-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.