192 PROCEEDINGS OF THE AMERICAN ACADEMY 



Four Iiuiidred and iiinety-tliird meeting. 



March 12, 1861. — Monthly Meeting. 



The President in the chair. 



Professor Horsford exhibited excellent drawings, by Mr. 

 Hand, of New York, of magnified dissections and preparations 

 of the grain of wheat, especially of the coats and superficial 

 portion or bran, which has been long since ascertained to 

 contain the principal part of the gluten, this indicating the 

 importance of retaining as much of the bran in the bread as 

 possible. 



Professor C. W. Eliot read the following paper : — 



Oh the Chromate of Chromium, and analogous Chromates, 

 with a New View of the Constitution of the Black Oxide 

 of Manganese. By Frank H. Storer and Charles W. 

 Eliot. 



I. Chuo.mate of Chromium (Cr^Oa CrOs). 



1. When a solution of monochromate of potash is mixed with a solu- 

 tion of any ter-salt of chromic oxide, the mixture immediately becomes 

 brownish red, a bright brown precipitate subsides, and when this pre- 

 cipitate has been completely deposited, the liquid separated by filtration 

 will present the clear yellowish-red color of bichromate of potash. The 

 chrome salt may be chrome alum, or sulphate of chromic oxide, or hy- 

 drated sesquichloride of chromium, and, if a sufficient excess of chro- 

 mate of potash be added to the solution, the precipitate and the filtrate 

 will present the appearances described. This filtrate may be evaporated 

 and crystallized ; the resulting crystals will be a mixture of bichromate 

 of potash and of sulphate of potash or chloride of potassium, as the case 

 may be : often crystals of monochromate of potash will also present 

 themselves. We prepared the precipitate for analysis by mixing a 

 solution of chrome alum with an excess of monochromate of potash. 

 The brown precipitate was washed with cold water : the color of the 

 wash-water, at first bright yellow, became gradually paler, but never 

 colorless. Twice in the course of the seven days during which the wash- 

 ing was continued, the precipitate was transferred from the filter to a 

 mortar, stirred up with water, and thrown upon a fresh filter. This pro- 



