CHROMIUM. 51 



of crystals, and consequently, susceptible of 

 exact analysis. The muriate is a beautiful green 

 solution, which may be evaporated to dryness 

 without losing its colour. The sulphate is a 

 dirty pale green powder, not soluble in water. 

 Neither nitric, phosphoric, or acetic acids gave 

 better results. 



To determine the nature of protoxide of chro- Atom of 



jj protoxide. 



mium I dissolved a quantity of chromate or pot- 

 ash in water, and added tartaric acid to the solu- 

 tion. An effervescence took place, and the so- 

 lution assumed a fine green colour, because the 

 chromic acid was converted into protoxide of 

 chromium. Ammonia being poured into the 

 green coloured liquid, the protoxide of chro- 

 mium was precipitated. It was collected on a 

 filter, well washed with water, and dried in the 

 open air. In this state it constituted a fine 

 green powder, exceedingly light, tasteless, and 

 dissolving with facility in acids. I could detect 

 no ammonia, nor tartaric acid, nor potash, in this 

 powder ; but found it a combination of water 26 hydrate 

 and protoxide of chromium. 33*75 grains ofid e pr 

 this hydrate were gradually heated to redness in 

 a green glass retort. Water was driven oft' 

 to the amount of 29*25 grains, and there re- 

 mained a fine green powder, weighing 4*5 grains, 

 and still in the state of protoxide of chromium ; 

 but it dissolves in acids with great difficulty, or 



not at all in several j because it is now anhy- 



D 2 



