Dr. T. Thomson ow Pyroxylic Spirit and its Compounds. 43 



being the discoverer. But I have been myself in the habit of 

 using it in lamps ever since 1816. And when I went to Glas- 

 gow in 1817, I found that it was prepared, for sale in that city, 

 by Messrs. Turnbull and Ramsay. It was, undoubtedly there- 

 fore, well known in this country long before 1822, the date of 

 Mr. Taylor's communication. 



When wood is distilled for the purpose of obtaining acetic 

 acid the pyroxylic spirit is formed and found in the aqueous 

 liquid which comes over. It is decanted off to separate it 

 from the tar which comes over at the same time. This 

 aqueous liquid being subjected again to distillation, it is in the 

 first tenth part of the product that we are to look for the 

 pyroxylic spirit. By repeated rectifications, it is obtained in 

 a state of considerable purity. The last rectifications must 

 be made over quick lime, partly to remove water and partly 

 some other impurities. The quantity of ammonia disen- 

 gaged when the lime is added, is considerable. This ammo- 

 nia was in combination with acetic acid. 



Pyroxylic spirit is pure when it does not become coloured 

 by exposure to the air and light, when it mixes with water in 

 all proportions without becoming muddy, and when it does not 

 form a black precipitate when mixed with protonitrate of 

 mercury, and has no action on paper stained with vegetable 

 colours. The quantity of it contained in the liquid obtained 

 by distilling wood is about 1 per cent. 



Mr. Kane, of Dublin, published an interesting set of expe- 

 riments on pyroxylic spirit in 1836*. He informs us that 

 he had begun the examination of it before the appearance of 

 Dumas's paper; and I remember hearing a paper on the 

 subject, read by him, at the meeting of the Biitish Scientific 

 Association at Dublin, in 1835. He purified the spirit by 

 saturating it with dry chloride of calcium. The saturated 

 solution crystallizes in long shining six-sided tables. He 

 distilled these crystals over the water-bath, as long as they 

 yielded spirit, and then adding water, continued the distillation. 



It is colourless, very fluid, and has a peculiar smell, at 

 once alcoholic and aromatic, and mixed with the odour of 

 acetic aether. 



neous aether (pyroxylic spirit) that any gentleman wishing to examine it 

 may know where to obtain it." Now if it had been used in lamps in 1816 

 it would have been perfectly ridiculous to have pointed out where it might 

 be obtained, ratber as a curiosity than for consumption, in 1822. — R. P. 



The date of the discovery has been put out of all doubt by an entry of 

 December 10, 1812, in the Process Book of the manufactory in which Mr. 

 Philip Taylor was then engaged, an extract from which has been sent us 

 by Mr. John Taylor, the Treasurer of the Geological Society. — R. T.] 



* Ann. der Pharmacie, xix. 164. [L. & E. Phil. Mag., vol. vii. p. 397 ; 

 X. 46. — Edit. 



