thought it might not be uninteresting to certain members of this Society to have the results of a series of experiments on a variety of pulps given in detail. If by so doing we contribute in any way to a better understanding of the matter, our work will not have been in vain.

The experiments were carried on during the last six or seven weeks, and we operated upon 14 different samples of pulp, many of which are lying on the table. The pulps used were

1. Swedish sulphite wood pulp.

2. Swedish sulphate wood pulp.

3. Swedish soda wood pulp, unbleached.

4. German sulphite wood pulp.

5. Mechanical wood pulp, cold process.

6. Mechanical wood pulp, hot process.

7. German sulphate straw pulp, bleached.

8. Swedish sulphite wood pulp, bleached.

Before we received the above samples they had all been lying for some time in an office in Edinburgh, and when they were handed to us on the 18th October last, they were in a comparatively dry condition.

9. Swedish sulphite wood pulp (another sample). Was received on the 26th October in a wet condition, and was allowed to dry spread out on a table in the laboratory for 24 hours, and was then treated along with the other samples.

10. Swedish sulphite wood pulp. 11. German sulphite wood pulp.

Had been in the laboratory some time; they had been sent as samples for moisture estimation, and had in consequence been at one time made bone dry and had also been torn to small pieces.

12. Swedish sulphite wood pulp (bleached). 13. Norwegian sulphite wood pulp (unbleached). 14. Norwegian mechanical wood pulp (cold process). These three pulps were weighed when received, and were at once put into a steam steriliser until thoroughly saturated. They had originally been wet samples.

From the 18th to the 23rd October the windows of the room where the pulps were placed were open, but as the increase in the weights was so slight, the windows were closed, and on the 24th to 27th a pan of water was kept boiling in the centre of the room in order to saturate the atmosphere with moisture. All the samples gained considerably in weight. After this, on the 28th October, they were placed in a steam steriliser, and steamed for three hours; then they were allowed to cool, and weighed rapidly. The weight now we assumed to be the maximum that could be obtained by pulps in an atmosphere highly charged with moisture. To confirm this, three of the samples were steamed a second time for three hours, but they did not materially increase in weight.

All the pulps were again exposed in the room with windows open, and weighed at intervals on the dates given in the table.

In all cases the pulps were exposed to the air standing on their edges so as to present as large a drying surface as possible.

On the 6th and 7th November the pulps were exposed for 24 hours in a warm room with much moistnre present and on the 8th November all the samples were made bonedry. Their weights were ascertained and the samples were again exposed to atmospheric influence in the ordinary temperature of a room for three weeks.

With only four days' exposure (after being made bonedry) to the ordinary temperature of a room in the month of November almost all the pulps had absorbed the maximum amount of atmospheric moisture they are capable of taking up, under normal conditions, from the air of a room, the temperature of which varies from 38° during the night to 60 during the day, and generally the the result of the investigation goes to show that, with the exception of the mechanical wood pulp, which absorbed from 10:03 per cent. to 11:58 per cent. of moisture, nearly all the other pulps absorbed less than 10 per cent. this it is evident that for sulphite, sulphate, and soda wood pulps, and also for straw pulps, atmospheric moisture may fairly be reckoned at 10 per cent., which is a limit over, rather than under, what they may be expected to absorb.

From

It is usual for the paper manufacturers of this country to receive from the pulp-makers abroad wood pulps containing from 50 per cent. to 60 per cent. of total moisture, and the custom of the trade is to base the price on what is known as " 50 per cent. air-dried pulp." The amount of moisture air-dried pulp is further assumed to contain varies from 10 per cent. to 12 per cent., depending on the terms arranged between buyer and seller, but this matter often gives rise to much difference of opinion and is the source of a good deal of misunderstanding. Would it not be more accurate, much more satisfactory, and be less liable to dispute if the price of all pulps was based on the absolutely dry substance? If such a basis as this was adopted it appears to us that all possible differences of opinion would vanish; assuming, of course, that the sample selected for the moisture estimation was a true and genuine representative of the bulk as received by the paper manufacturer.

Take one example: Suppose 201. per ton was the price agreed upon for absolutely dry pulp, and that the latter, after careful sampling and estimating the moisture, was found to contain :

By simple rule of three the price would come out at 81. per ton. At present the system adopted is (as those engaged in the industry are well aware) much more complicated. One example will make this apparent. If the price arranged for pulp, containing 50 per cent. of air-dried pulp, is, say, 107. per ton, and if it is further agreed that airdried pulp shall be assumed to contain 10 per cent. of moisture, we have the following calculations to make, after ascertaining the total moisture, thus :—

The price fixed was 101. per ton for 50 per cent. airdried, and as the analysis shows only 44 44 per cent., the price is proportionately less, or 81. 17s. 7d. per ton.

You will observe on the table on which our results are recorded, that we took the readings on a dry and wet bulb hygrometer, the former, i.e. the dry bulb thermometer, gives the temperature of the air; the other gives a reading several degrees below the air temperature, but when air is saturated the readings are alike.

The dew point was obtained from Glaiser's formula.

As the sampling of the pulp to get a genuine specimen of what accurately represents the bulk lying at the mills of the paper manufacturer, is a somewhat difficult matter, and as inaccurate results are very likely to result if the pieces selected for moisture estimation are much handled or exposed even for a short time to atmospheric influences, we have now adopted the system of taking large samples, placing them, immediately they are removed from the bales and without tearing up to small pieces, in a tared copper cylinder, which is closed with an air-tight lid. On reaching the laboratory the gross weight of the cylinder is accurately taken, and the entire sample is dried in a large water-oven constructed for the purpose.

Lately, the disputes that have arisen in regard to the moisture allowance in air-dried pulp have caused the Norwegian and Swedish Cellulose Pulp Association to fix upon 12 per cent., that is, that 100 kilos. of air-dry cellulose shall contain 88 kilos. absolutely dry pulp and 12 kilos. water (see Chem. Tr. J., 22nd July 1893, 51). May we

not rather look forward to the time when, as we indicated before, the pulp maker will fix a price based on the dry cellulose present.

DISCUSSION.

Mr. G. T. BEILBY pointed out that the amount of atmospheric moisture varied from day to day, and asked what was the limit of variation in the absorbing power of the pulp.

Dr. J. B. READMAN: At the most 2 per cent.

Mr. R. IRVINE cited an instance in his own experience of a large cargo of rags which had been damaged by seawater. He found, on testing them, that they contained 10 to 11 per cent. of moisture. He at first had assumed that this moisture was alone due to the sea-water accidentally introduced during the voyage. The question had become a serious one, as the paper-maker had concluded to deduct 10 per cent. from the price of the rags. In blank experiments, however, conducted on rags which had not been subjected to the damaging action of sea-water, he was surprised to find that the moisture differed by only half a per cent. from that in the damaged samples.

Mr. W. IVISON MACADAM said he had lately experimented on tweeds, both pure and with cotton present, and he had found the average proportion of water absorbed by these fibres to be from 8 to 13 per cent. In both classes of tweeds there was the usual oil present.

Mr. IRVINE remarked that a coating of oil had therefore apparently no effect on the amount of moisture absorbed.

The CHAIRMAN considered that in estimating the amount of moisture, the absolutely dry material should be taken as the standard.

Dr. J. B. READMAN, in reply, emphasised the necessity of promptly securing samples. In an instance within his knowledge, the material had lost 0.2 per cent. after being exposed for 15 minutes to the air of an ordinary room. 0.2 per cent. was too large an amount to neglect in cargoes of 500 to 1,000 tons. Every precaution ought to be taken in order to obtain a large representative sample, and no time should be lost in securing it in a hermetically-sealed vessel such as that which he exhibited.

MANUFACTURE OF OIL-GAS.

BY JOHN LAING, F.I.C., ETC.

THERE are three convenient methods by which mineral oil can be readily decomposed, viz., by repeated distillation into self-by radiant heat-and by distilling under pressure. In the system which I now bring before your notice for the manufacture of oil-gas, I employ a combination of these three methods working in harmony together. Mineral oilgas making is nothing more than the "cracking" operation carried on to extreme. The apparatus consists of an oil still charged with a quantity of oil consistent with the number of cubic feet of gas it is desired to be made. This oil is vaporised by heat either direct from a furnace for itself, or by using the surplus heat from coal retorts, where they are in use. The oil vapours, as they leave the still, pass into a condenser so arranged that the more condensible portion on being liquefied returns immediately to the still for re-distillation and condensation; the lighter portion passes over and down into a superheater, and then, coming into close contact with the radiant heat found there, is further decomposed and rendered into permanent gas of very high illuminating value. The back pressure on the still, from the gas-holders, raises the boiling point of the oil in the still, and thus assists in its decomposition.

Between the still and the condenser I place an arrangement which acts as a water trap, so that should any water happen to get into the still with the oil it will be removed without any trouble or fear of accident. If this water trap was not employed, then the steam from the still would condense in the condenser overhead, and this water, returning to the still (which is now at a higher temperature), would suddenly burst into steam, and might prove dangerous.

This trap catches all the condensed material from the condenser, and should water be present it will fall to the bottom because it is heavier than oil; the overflow of oil from the surface returns to the still perfectly free from water, and during the remainder of the distillation there is no possibility of further trouble or anxiety on account of water in the still. This trap is fitted with a cock at bottom, and when you turn it on and find oil, you may rest assured that no water is present to be dealt with. Sometimes it happens that water is present in the oil tanks from which the oil is barrelled, and if the tank is well run down some water may have got into the barrels along with the oil unperceived. In this way water may find its way into a still when being charged from the barrels or tank, but with the arrangement I have here mentioned no harm can result from its presence.

In the form of superheater I am using at present I have a number of discs with holes punched through one half of its surface, and the edges of the discs are vandyked or nicked. These discs are fitted on to an iron rod at regular intervals from each other; the end disc has its holes downwards, the next one has its holes upwards, and so on to the end, thus giving the gas a zig-zag travel, and making it come in closer contact with the radiant heat in the superheater. My reason for giving the gas this zig-zag travel is to ensure a uniform quality of gas being made. If you merely pass the gas through an empty superheater direct, then that portion of it which is nearest the sides of the vessel is decomposed the most; the central portion is of a heavier nature, and I am strongly of opinion that this mechanical mixture of the molecules (if I may use such an expression) is one great cause why some makes of oil-gas smoke so badly on being consumed in the burners. If the hydrocarbon molecules are of a uniform character, then you will have a gas which will give satisfactory results on being consumed. I am quite aware that a proper size of burner should be employed for consuming very rich gases. but what I mean to convey is that using two makes of oil-gas, and consuming them side by side under the same conditions in every respect as to burners, pressure, &c., you will find that the gas which has been the result of uniform decomposition will give more satisfactory results than the gas which is not so uniform in its composition, and being more a mechanical mixture of its component parts than a chemical one. Oil-gas of uniform composition blends immediately with coal-gas, and I believe has no tendency to layering in large holders, and accordingly you should have no variation of illuminating value from different heights of the gas-holder. Some people seem to think that oil-gas does not store well, and that it loses a deal of its illuminating power if it has to travel far. Now this is quite a misconception, for really the fact is that if oil-gas is properly made it will store better, and travel better, and stand cold better than coal-gas will, for coal-gas depends more on condensible vapours for its illuminating power than oil-gas does.

The lower temperature at which you can make permanent oil-gas the better results you obtain. You get a higher illuminating gas, less deposit of carbon, and you get a larger quantity of gas from your oil than if you are decomposing your oils at higher temperatures.

By my process, all the dirt is left in the still, and in time produces a pitch of first-class quality; this pitch being liquid whilst hot, is readily run from the still by an arrangement provided for that purpose, and leaves behind practically a clean still ready for the next charge. Before running down the still bottom it should be sampled first, and if the condition is too soft when cold, that indicates that you can yet take more oil from it, and by leaving it longer under heat you will obtain all the more gas and a

3. It saves a deal of cleaning of stills.

4. It can be stored anywhere and for any length of time without deterioration.

5. It is of higher commercial value.

If you take a red-hot still and trickle in slowly, say one gallon of oil, and allow the vapours to escape through a sealed condenser of three inches water, you will have a larger amount of coke formed than if you distilled down the same quantity of oil from a charged still with oil under the same conditions. You will thus see that the quantity of pitch obtained by my method of oil-gas manufacture is less in proportion to the amount of coke formed by other high temperature processes. Coke is a worse conductor of heat than pitch is by a long degree. It is no uncommon thing to see a still bottom bright red-hot with a layer of coke at

the bottom and several inches of pitch on its upper surface, and yet the pitch was not strongly giving off vapours.

I may here mention that I have arranged a special pitch cock which will save a deal of trouble by its being easily kept free from plugging up. In the ordinary cocks at present in use, the box or hole in the plug of the cock often retains some of the pitch, and as it cannot escape when the barrel is turned off, it remains and hardens there, and, before another run down can be made, time must be allowed for the hot pitch behind the cock to melt out the plug in the cock-barrel. This is sometimes rather difficult to get over, and a steam jet has to play on it for some time before it will clear. To get over all this I got a cock specially made with a "pap" cast on the one side of it; a hole was bored through this into the plug box, so that when the plug was turned off a hot wire can easily be passed into the hole and all the pitch cleared out. A screw plug fits into this hole. It might, perhaps, even be further improved by having a "pap" cast on both sides and a hole in it so that a hot wire could pass right through and through, and thus clear the cock with the greatest ease. This method is extremely