16 W. RB. Nichols on the Chromites of Magnesium. 
distillate ere any considerable increase in the temperature 
of distillat 
I hope ae some future day to be able to fractionate both the 
crude California petroleums, and the products of their distilla- 
tion under pressure, and thus obtain some additional facts in 
reference to this interesting question. 
Cambridge, Mass., Nov. 9th, 1868. 
Arr. IIIl.—On the Chromites of Magnesium ; by W. R. Nicu~- 
ous, student at the Massachusetts Institute of Technology. 
Tue extent of the power possessed by some of <i hydrated 
sesquioxyds, notably by the hydrate of chromi o hold 
magnesia and several other of the metallic preoiyai' in insolu- 
ble combination, appears never to have been distinctly recog- 
nized by chemists. Fresenius, it is true, remarks * that sesqui- 
oxyd of chromium cannot be separated (quantitatively) by 
ammonia from the aliatine earths, since, even though carbonic 
acid be completely excluded, portions of the alkaline earths are 
thrown down in combination with the sesquioxyd of ¢ 
5 
But his co is far less forcible than the facts in the cade 7 . 
demand, 
Other inittien have fallen into the grave error of supposing 
that magnesitim can be separated from chromium, with suffi- 
sis. According to Galloway, this ammonia precipitate is col- 
lected by itself and examined for iron, aluminum and chro- — 
mium ; sulphid of ammonium is then added to the filtrate to — 
throw sca cobalt, nickel, zinc and manganese ; carbonate of 
would. be are ee imy be fs in miany cases to detect inmate 
hen — = presence of chromium, From a solution con- — 
- ‘itati ee ‘Chemical eee 3 4th ei London, 1865, 231 a. 
ed. London, ok x et seq. 
