328 



Mr. W. J. Sell and Prof. W. J. Lewis. [Feb. 14, 



substances at about 60 C. The nature of this change is at present 

 under investigation. 



In addition to the foregoing, the following new compounds have 

 been examined : 



The Chromate. 



This compound separates from a warm saturated solution of tlie 

 dichromate, cautiously neutralised with ammonium carbonate, in long 

 dark-green needles. The crystals are very efflorescent, and rapidly 

 become opaque from loss of water. They are sparingly soluble in 

 cold, more readily in hot water, undergoing at the same time slight 

 decomposition, with separation of brown flocks of chromic chromate. 

 The salt is insoluble in alcohol, ether, carbon disulphide, and benzene, 

 and has the composition (COITOI^CrWrO^ETO. 



The following results were obtained on analysis. The salt was 

 dried by pressure between bibulous paper : 



1. 0*3274 gram salt lost in vacuo 0'0196 gram H 2 0. 



2. 0-3274 ignited left 0'0994 gram Cr 2 3 = 30' 36 per 



cent. Deducting Cr existing as CrO 3 , leaves 11 '94 Cr 3 3 , or 

 8'18 per cent. Cr. 



3. 0-5465 gram salt lost at 100 C. 0*03315 gram H 2 0. 



4. 0-5465 ignited gave 0*16585 gram Cr 2 3 = 30' 34 per 



cent. Subtracting Cr existing as CrO 3 leaves 1T92 Cr 2 3 , or 

 8-17 per cent. Cr. 



5. 0*4774 gram salt, dissolved in dilute HC1, excess of KI added, 



and the iodine estimated by thiosulphate, required 35*62 c.c. ; 

 each c.c. thiosulphate = 0'0032459 CrO 3 . 



The Bromide. 



This compound is conveniently prepared from the dichlorchromate 

 by first forming the very soluble acetate by double decomposition 

 with lead acetate, filtering off the mixture of lead chromate and chlo- 

 ride, and precipitating the bromide from the filtrate by dissolving in 

 it crystals of potassium bromide. The drained and washed precipi- 



