226 PROCEEDINGS OF THE AMERICAN ACADEMY 



quired temperature he obtained a black mass which had taken the 

 shape of the crucible ; this he powdered and digested with water, with the 

 expectation of dissolving that portion of the chromic acid which had not 

 been affected by the heat ; the wash-water after some days still remain- 

 ing yellow, he concluded that the substance itself gradually dissolved, and 

 proved this to his own satisfaction by analyzing two portions, one of 

 which had been washed more than the other, with the same result, viz. 

 57.93 per cent of chromium and 42.07 of oxygen. These figures cor- 

 respond to the formula CrjOs 3 CrOs- Now chromic acid contains 

 52.23 per cent of chromium and chromic oxide 08.02 per cent, and in 

 changing fi-ora the first into the second, under the influence of a mod- 

 erate heat, the heated substance will at some moment contain 57.93 per 

 cent of chromium ; before that moment it would contain less, after that 

 moment more. "VVe were not so fortunate as to hit on the right time 

 for stopping the experiment. We subjected a mass of chromic acid to 

 a temperature a little above 250° for three hours, and obtained a brown- 

 ish black substance, such as Traube has described, which, powdered 

 and boiled with water, imparted a faint yellow color to the liquid. 

 Analysis showed that it contained 54.12 per cent of chromium. It is 

 quite clear that any substance prepared in such a way must be a mix- 

 ture, and that the particular mixture analyzed by Traube has no claim 

 to the name and formula of a definite compound. 



Still another hypothetical chromate, called " Soluble Brown Chromic 

 Oxide or Acid Chromate of Chromic Oxide," figures in Gmelin's Hand- 

 book (loc. cit.). Maus and many others have made a solution of hy- 

 drated chromic oxide in aqueous chromic acid, but Maus alone has 

 analyzed the solution; we have already expressed our opinion that the 

 liquid he analyzed was only an indeterminate mixture (p. 211). The 

 observation and the conjecture of Berzelius, cited by Gmelin in this 

 paragraph, we have already remarked upon ; the precipitate which 

 Berzelius speaks of is the chromate of the formula Cr^Os CrOs. 



To sum up the case, — there is not a particle of evidence of the ex- 

 istence of any chromate of chromium containing more than one equiva- 

 lent of chromic acid. Such may be hereafter discovered, but it does 

 not seem probable that they will be found to be insoluble compound?. 

 Until the realities are made known to us, why cumber the science with 

 names and formula?, which fill no gaps, extend no analogies, bridge no 

 difficulties, but are merely a perplexity and a hinderance ? It has been 

 too much the custom to call the chromate of the formula CroOo CrOs 



