388 MR C. G. WILLIAMS RESEARCHES ON 



solution of chromic acid being quite dissimilar, for while chinoline and its salts 

 gave a beautiful orange-yellow crystalline precipitate, leukol was oxidized and con- 

 verted into a black resinous oil. Subsequently,* Liebig announced, upon the au- 

 thority of experiments made by Hofmann, that perfectly pure leukol gave the 

 same crystalline precipitate with chromic acid. I have not been so successful as 

 M. Hofmann ; for, although the chinoline and lepidine procured by destructive 

 distillation from cinchonine have, in my hands, given salts of extreme beauty and 

 purity with chromic acid, I have failed to obtain the same result with either the 

 chinoline or lepidine from coal-tar. I have also boiled the bases from the latter 

 source with dilute chromic acid, to destroy impurities, and then separated them by 

 distillation with potash, but they merely gave an oily precipitate with chromic acid. 

 When dissolved in hydrochloric acid, and bichromate of potash is added, the same 

 result occurs. I even took a platinum salt of coal-lepidine, which yielded, on com- 

 bustion, the numbers detailed in Analysis I., p. 398 ; and, after having reobtained 

 the base by distillation with potash, endeavoured to procure from it a crystalline 

 chromate, but in vain, a red oil being the only product. It is true, that when I 

 added dilute chromic acid to chinoline from coal-tar, the sides of the tube acquired 

 a coating of very minute brilliant points, which reflected light with a peculiar 

 satin-like lustre ; but the lens resolved them into oily globules. The following 

 experiments were, therefore, made upon chinoline from cinchonine. Neither Ger- 

 hardt nor Hofmann have analysed the salt. 



The beauty of the bichromate of lepidine described in my last paper,f induced 

 me to ascertain the composition and properties of the homologue next below it, 

 in the anticipation that its outward appearance would be equally striking. But 

 there are some slight differences in the two bodies ; bichromate of chinoline is 

 still less soluble than the other salt, and this prevents the crystals from being 

 readily procured of so large a size. When dry, it is much more violently decom- 

 posed by heat than the lepidine compound. The fixed product is, however, the 

 same, namely, green oxide of chromium and carbonaceous matter. If the dry 

 salt be placed in a capsule, and heat be very gradually applied, no change at first 

 takes place, but suddenly it takes fire with explosive violence, and the greater 

 part of the green oxide and carbon is projected. I prepared the salt for analysis 

 by adding dilute chromic acid in excess to pure chinoline ; at first the product is 

 somewhat resinous, but immediately it is touched with a glass rod, it becomes 

 gritty and crystalline. The solid is then filtered off, the mass slightly washed, 

 dissolved in boiling water, filtered to remove traces of an oily impurity, and, on 

 cooling, the fluid becomes filled with brilliant yellow needles arranged in groups. 

 It may be dried at 212° with safety, provided adhering moisture has been re- 

 moved as much as possible by pressure between folds of filtering paper. If the 



* Chem. Gaz., vol. iii., p. 251 (1845). Proc. of Chem. Soc, April 7, 1845. 

 f Trans. Roy. Soc. Edin., vol. xxi. part ii. 



