54 On the Combinations of fixed Oil with 



The theory of the action seems to be, that part of the acid 

 sutlers decomposition ; nitric oxide and nitrogen being dis- 

 engaged and the lard becoming- oxygenized. This oxygenized 

 lard combines with another portion of dry nitric acid ; the water 

 which it contains being separated, and exerting an attraction 

 for the remainder of the acid, as strong as that of the lard, 

 prevents it from suffeiing any farther change. The compound 

 I conceive, therefore, to bea nitrate of oxygenized lard, bearing 

 the same relation to lard which the metallic nitrates do to the 

 metals. 



When nitric acid, holding in solution nitrate of mercury, is 

 used, the lard acquires a brown colour, which increases in 

 intensity till nitric oxide ^as is disengaged, when it changes to 

 a lively yellow, and a fluid subsides as in the former case, 

 which is weak nitric acid, holding in solution nitrate of 

 mercury. One drachm of red oxide of mercury was dissolved 

 in two drachms of nitric acid, and afterwards was combined 

 with ten drachms of lard. From this one drachm of liquid was 

 obtained, which, with an additional quantity obtained by wash- 

 ing the compound, gave a precipitate with ammonia, which 

 weighed twenty-three grains; therefore, as in the former case, 

 a quantity of nitric acid remained uncombined, so here n 

 portion remains, holding in solution a proportionate quantity of 

 nitrate of mercury. 



From the manner in which the oxide of mercury was here 

 combined with the nitric acid, there was no nitric oxide con- 

 tained in it, but if a stream of nitric oxide is passed through 

 the solution, or if the acidulous peroxide is made by dissolving 

 mercury in nitric acid, then the nitric oxide communicating 

 oxygen to the, lard, at once forms with the solution a compound 

 of a yellow colour ; or, if the lard is previously combined with 

 a portion of nitric acid before adding the nitrate of mercury, 

 the same result is obtained ; it appears to me, therefore, to be 

 a compound of nitrate of mercury, with nitrate of oxygenized 

 lard. The common name 'ointment of nitrate of mercury ' 

 serves well to distinguish it; the compound of nitric acid and 

 lard might with propriety be called 'nitrated lurd.' 



The state of combination in which the mercury exists, de- 

 pends upon the manner in which the compound is formed; 

 whfn the compound is formed by dissolving red oxide of 

 mercury in nitric acid, it contains peinitrate of mercury only. 

 When the mercury is dissolved in nitric acid as directed by the 

 Colleges, the solution contains both pernitrate and pronitrate. 

 In preparing the ointment of nitrate of mercury for medical 

 purposes, as it is directed to be stirred till it is cold, the un- 

 combined acid, and the nitrates which it retains, remain diffused 



