Dr. Kane on Pyroxylic Spirit. 45 



hypotheses which Fresnel successfully employed in solving ths 

 problem of reflexion from ordinary media. These hypotheses, 

 therefore, are not sufficient when a})plied to ciystals ; except, 

 indeed, in the case before alluded to, where the azimuth = 0, 

 which l)as been solved by M. Seebeck. It should be observed, 

 that though the reasons which I have assigned for the prin- 

 ciple of equivalent vibrations are extremely simple, yet it was 

 not by such simple reasoning that I was led to it originally. 

 Trinity College, Dublin, Dec. 13, 1836. 



XII. Researches in Organic Chemistnj, — First Series, Contri- 

 butions to the History of Pyroxylic Spirit and of its derived 

 Combiiiations. By Robert J. Kane, M.Z)., M.RJ.A,* 



'\/i Y residence in Giessen during the summer of the present 

 •^^■'- year [1836] allowed me to continue under the guidance of 

 Professor Liebig the examination of pyroxylic spirit^ and the 

 compounds obtained from it, which I had commenced prior to 

 my becoming acquainted with the results of Dumas and Peligot, 

 and of which a portion was presented to the British Associa- 

 tion assembled in Dublin during August 1835t. 



As sent into commerce pyroxylic spirk is contaminated by 

 the presence of a volatile oily material, from which it is ex- 

 tremely difficult to obtain it free. Dumas states that the 

 impurities are completely separated by distillation with fresh- 

 burned lime, a process which in my hands at least has never 

 perfectly succeeded. The pyroxylic spirit thus obtained is al- 

 ways rendered milky by admixture with water, and conse- 

 quently unfit for accurate examination. Caustic potash and 

 sulphuric acid were found equally unsuccessful in removing 

 this impurity, from which, however, the pyroxylic spirit is ob- 

 tained free by the following simple process. 



Chloride of calcium being dissolved in pyroxylic spiritin con- 

 siderable quantity, so much heat is evolved that the liquid if 

 in considerable mass rises to its boiling point, and on cooling 

 there is deposited a compound of pyroxylic spirit with chlo- 

 ride of calcium in large brilliant six-sided tables, like those of 

 acetate of zinc. This compound requires for its decomposi- 

 tion a temperature much higher than that of boiling water. 

 If therefore, the rough pyroxylic spirit be saturated with 

 chloride of calcium and distilled, the excess of spirit and the 

 oil come over, and are collected as long as by temperature 

 of a water-bath the distillation conthiues. When this has 



* Communicated by the Author. 



f [An abstract of Dr. Kane's paper presented to the British Association, 

 will be found in Lond. & Edinb. Phil. Mag., vol. vii. p. 397, and a notice 

 of the results obtained by MM. Dumas and Peligot at p. 427 of the same 

 volume, of which see also p. 395. — Bdix.] 



