On the Combinations of Chromium, 139 



salts of lead. When heated on a vapor bath for some hours, 

 it is rendered partly insoluble, water boiled on it gives a 

 brown solution containing nitric acid. At a temperature be- 

 low redness it is decomposed, and becomes a very bulky 

 green oxide. 



Hydrosulphuric acid, does not decompose solutions con- 

 taining protoxide of chromium, nor does oxide of chromium 

 dissolve in its solution. 



Muriate of Chromium. — When dry, this salt exists in the 

 state of a transparent green powder ; its solution is dark green, 

 and of a sweet astringent taste ; it does not yield crystals. 

 If heated to 212° this salt exhibits some greenish grey spots; 

 at 300°, no acid is disengaged. When dried at 212° it is 

 slightly deliquescent. At a red heat it swells, becomes green- 

 ish gray, and is ultimately decomposed. 



Sulphate of Chromium. — Diluted sulphuric acid dissolves 

 oxide of chromium, and forms a neutral green solution of an 

 astringent taste, — it is uncrystalizable. When dry, its frag- 

 ments are blue, green and transparent ; mixed with charcoal 

 and heated in a closed crusible, it affords a green powder, 

 which, with muriatic acid gives an evanescent odour of hy- 

 dro sulphuric acid ; the acid is merely tinged with green. 

 When nitrate and sulphate of potash exist in the solution, 

 by evaporating and cooling, the nitrate ciystalizes in very 

 oblique octohedrons, or double 4 sided pyramids with rhom- 

 bic bases, — of an apple green color. 50.20 grains of sul- 

 phate of chromium, dried at 212° F., dissolved in water, 

 and added to an excess of a solution of muriate of baryta, — 

 gave 65.70 grains dry sulphate of baryta =22.27 sulphuric 

 acid. The filtered solution, treated with a solution of sul- 

 phate of soda and again filtered, decomposed by carbonate of 

 ammonia, — gave 15.98 grains dry oxide. 22.27 + 1 5.98 -f- 

 1 1.95 water in the salt=50.20. And 22.27 : 1 5.98 : : 40 : 28.70. 



Phosphate of Chromium. — Phosphate of soda, added to ni- 

 trate of chromium, occasions a precipitate of phosphate of 

 chromium ; while moist, its color is light green, by drying it 

 becomes darker and after being heated red hot, it is blueish 

 black ; its powder is greenish brown, and it is soluble in hot 

 muriatic acid. In phosphoric acid it remains suspended for 

 some days, but finally subsides, 



