138 EXPERIMENTS AND OBSERVATIONS, &C. 



particularly when aflifted by heat, ads readily upon the cry* 

 ftalline matter ; during the procefs there is a difengagement of 

 nitrous gas. A fmall quantity remains diflblved in the fluid, 

 and may be precipitated from it by potafh. The greateft part 

 however rifes to the furface as the fluid cools in the form of 

 drops of oil, which gradually grow concrete ; the cryftalline 

 texture is deftroyed, and its confiftence refembles that of a 

 Sed U fub° f thC ve S etable refi n • Water does not dilTolve this peculiar matter, 

 ftances. bat it feems to render it fomewhat more brittle and friable. 



Alcohol aflifted by a gentle heat diflblved it ; it was precipi- 

 table from the folution by water in the form of a grey powder. 

 Ether, at the temperature of the almofphere, diflblved it ra- 

 pidly ; water precipitated it from the ether in the form of 

 drops of oil. When the fluid was evaporated, it was depo- 

 iited, without exhibiting any marks of a cryftalline ftru&ure. 

 Cauftic potafh acled upon it without the afliftance of heat, 

 when boiling it diflblved it with more facility ; the fluid ac- 

 quired a reddifh brown hue ; it was not precipitated by water, 

 but the fulphuric acid feparated it in the form of a grey pow- 

 der. The action of ammoniac was nearly fimilar, though as I 

 conceived, fomewhat more powerful than that of the fixed 

 alcalis. The folution was alfo of a reddifli brown colour; but 

 the precipitate by fulphuric acid was of a bright yellow. It 

 appears therefore that the matter of biliary calculi has its pro- 

 perties materially changed by the operation of the nitric acid. 

 It entirely deftroys its cryftalline tendency, and renders it 

 more foluble in ether and in the alcalis. It has been fuppofed 

 that by this procefs it becomes more aflimilated to the adipo- 

 refin of the bile *, but it ftill differs from it in not poflfefling 

 any degree of folubility in water f . 

 The fubftanccs Thefe remarks upon the cryftalline matter of biliary calculi, 



rea^y^ffertnt! ^ ew that there are ^ evera ^ important circumftances in which 

 it differs both from fpermaceti, and from adipocire, to both of 

 which it has been compared J. Upon the whole, though the 



* Powel, p. 121. 



f Ann. de Chimie, torn. vii. p. 178. Encyc. Meth. Chimie, 

 art. Bile, p. 566. 



J I may obferve that the dark-coloured particles which were dif- 

 perfed through the cryftalsof the calculus, though they might have 

 been originally compofed of infpiflated bile, did not retain the pro- 

 perties of this fubftance, as they were nearly infoluble both in boil- 

 ing water and in alcohol. 



five 



