400 SALTS 



quantity of moisture present is merely hygro- 

 metrical. Doubtless the true constituents of 

 this salt are 



1 atom chromic acid 6' 5 



1 atom protoxide of mercury v 26 



32-5 



The reason why the weight of the protoxide of 

 mercury appears less than the truth, is that a 

 certain portion of it was reduced to the metallic 

 state during the drying. This likewise increased 

 the apparent quantity of water, by occasioning 

 a loss. 



Protace- J. Protacetate of mercury. This salt is imme- 

 diately deposited in beautiful silky scales, when 

 solutions of nitrate of mercury and acetate of 

 soda are mixed together. It has the disagreea- 

 ble taste of the mercurial salts ; but. it is the least 

 soluble of all the acetates, requiring about six 

 hundred times its weight of water to dissolve it. 

 On this account, nitrate of mercury may be em- 

 ployed as a good reagent to discover the pre- 

 sence of acetic acid in saline solutions. If the 

 quantity of acetic acid present exceed Tnmth of 

 the weight of the liquid, the silvery scales of 

 acetate of mercury almost always present them- 

 selves. 10 grains of these scales being digested 

 in a flask with caustic potash gave 6*98 grains 

 of protoxide of mercury ; hence, the acid and 

 water in these 10 grains amounted to 3'0% 



