334 PHILOSOPHICAL TRANSACTIONS. [ANNO 1783. 



heat of 110°. The solution, however, becomes turbid in a few days. The 

 calces of antimony are soluble in a much less degree. 



Regulus of antimony in marine acid. — 100 grs. of spirit of salt, whose specific 

 gravity is 1.220, dissolve about 1 gr. of regulus, with the assistance of a slight 

 heat. Spirit of salt, whose specific gravity is 1.1/8, also acts on it, but dis- 

 solves still less. I believe the concentrated acid would, in a long time, and with 

 the help of a gentle heat, dissolve much more of it. The calces of antimony 

 are much more soluble in this acid. 



Regulus of arsenic in vitriolic acid. — 200 grs. of oil of vitriol, whose specific 

 gravity is 1.871, dissolve 18 of regulus of arsenic in a heat of 250 u . Of these 

 about 7 crystallize on cooling, and are soluble in a large quantity of water. 

 The calces of arsenic are more soluble in this acid. 



Regulus of arsenic in nitrous acid. — 100 grs. of this semi-metal require 140 

 grs. of real nitrous acid, whose proportion to water is as 1 to 11, and the assist- 

 ance of heat. It is soluble in a less or more concentrated acid, but in a lesser 

 degree. This solution affords 102 cubic inches of nitrous air. The barometer 

 at 30, and the thermometer at t)0. The calces of arsenic are also soluble in 

 this acid. 



Regulus of arsenic in marine acid. — 100 grs. of spirit of salt, whose specific 

 gravity is 1.220, dissolve 14 grs. of regulus of arsenic; the marine acid, in its 

 common dilute state, that is, whose specific gravity is under 1.1 7, does not at 

 all affect it. The calces of arsenic are less soluble in this acid than in the vitriolic 

 or nitrous. 



The advantages resulting from these inquiries are very considerable, not only 

 in promoting chemical science, which, being a physical analysis of bodies, essen- 

 tially requires an exact determination, as well of the quantity and proportion, as 

 of the quality of the constituent parts of bodies, but also in the practical way. 

 Thus, in the first place, it is well known, that several important processes are 

 very inaccurately described by ancient chemical writers, and even by some of a 

 modern date: they frequently, for instance, describe the acid they employed by 

 reference to the quantity of fixed alkali, earth, or metal, a given quantity of such 

 acid was capable of neutralizing or dissolving. Now the foregoing observations 

 immediately inform us of the quantity of real acid capable of performing that 

 effect; the remainder, therefore, must have been water; and the quantity of 

 real acid and water being known, the specific gravity is easily found by the help 

 of the foregoing tables, and thus an acid of the same strength may be formed. 



2dly. The importance of this knowledge in the art of pharmacy is very ob- 

 vious, especially with regard to medicines formed of metallic substances, whose 

 powers depend on the proportion of their ingredients, and their action on each 

 other. 



