230 ANNUAL OF SCIENTIFIC DISCOVERY. 



the size of the conduit might be varied so as to allow the tar-like bodies to 

 form, or to prevent their appearance, at pleasure. 



But a more remarkable result was obtained when, after having prevented 

 the production of heavy hydrocarbon fluids, the influence of reduced size of 

 tube was studied in its relation to the composition of the gas afforded by a 

 peculiar kind of coal. To a certain extent, the chemical constitution of the 

 gas formed was found to be under control, and the conclusion reached was, 

 that dissimilar permanent gases may be thus obtained from the same parcel 

 of coal without a modification of temperature. 



Any explanation of the change of composition induced in the volatile 

 parts of bituminous coals under the above-described conditions, should not 

 include mechanical pressure, which is no greater than often exists in ordinary 

 cases. 



It seems probable that the presence of an atmosphere of nearly permanent 

 gases in the decomposing vessel, and the regular continuous flow of them 

 from the coal, prevent the formation of heavy vapors at the instant of change 

 in the coal. In support of this point, we find the temperature necessary to 

 convert coal into gas without the presence of heavy hydrocarbons much less 

 high than when they were produced. 



We may, therefore, observe the decomposition of coal without the simul- 

 taneous formation of tar, and beds of coal may be converted under existing 

 natural conditions to anthracite, without secondary products being formed. 



ON THE DECOLORIZATION OF ROSIN. 



At a recent meeting of the Royal Institution, London, Mr. Mercer exhibited 

 a specimen of purified and bleached rosin, a substance, he said, which at 

 first might not appear to be of much interest or importance, but the bleach- 

 ing of rosin was a subject which had occupied the attention of the most 

 eminent chemists, and hitherto without success. Now, however, the problem 

 had been solved, and a patent taken out by Messrs. Pochin and Hunt, of 

 Manchester, by which common black rosin, worth only 4s. 6d. per cwt., was 

 converted into a beautiful white article, worth 18s. per cwt. To obtain this 

 result, the rosin to be purified was placed in a still with a receiver, and a, 

 steam-pipe in connection with a boiler was introduced into and reached to 

 the bottom of the still, where it radiated with various smaller pipes, perfo- 

 rated so as to allow of the exit of steam. The steam was heated until the 

 rosin melted, when steam was admitted and thoroughly permeated the en- 

 tire contents, the temperature of the still being at the same time raised to - 

 600, at which it was maintained until all the contents of the still capable of 

 being volatilized had passed into the receiver, the contents of which, at the 

 close of the operation, would be found to consist of fluid and solid matter, 

 the former being principally water, and the latter the bleached rosin, holding 

 a quantity of moisture in suspension. After the water had been driven off 

 by remelting, the rosin had the beautifully white and transparent appearance 

 of the specimen on the table. 



SAPONIFICATION OF FATS BY CHLORIDE OF ZINC. BY LEON KRAFFT 



AND TESSIE DU MOTTAY. 



When any neutral fatty matter is heated with anhydrous chloride of zinc, 

 we see it melt and disappear gradually as the temperature rises. Between 



