32 PROCEEDINGS OP THE AMERICAN ACADEMY 



Tliese were first analyzed and described in nay laboratory by Sadtler, 

 who found for the luteocobalt salts the formula, — 



Co,(NH3),,(NO,)„+Co,(NO,),,+OH,. 



In resuming the study of this subject, I found the method of j^irepara- 

 tion at first ado[)ted somewhat uncertain, because the excess of the alka- 

 line nitrite acts readily upon the cobaltamine, formhig other products 

 not always easy to separate. The following method gives better re- 

 sults. One molecule of any soluble salt of the cobaltamine — the 

 nitrates are to be preferred — is to be dissolved with two molecules of 

 cobaltic chloride or nitrate, and a little acetic acid. A solution con- 

 taining as nearly as possible twelve molecules of sodic nitrite is then to 

 be added. The luteocobalt salt is precipitated almost immediately ; 

 the corresponding salt of roseocobalt after a short time. 



The salt of luteocobalt obtained in this way is a yellow crystalline 

 body very slightly soluble in cold water, and easily purified by wash- 

 ing. Boiling water dissolves it in very small quantity, giving a pale 

 yellow solution. I have usually obtained it in rather larger deep 

 orange granular crystals by adding a solution of the corresponding 

 much more soluble roseocobaltic salt, Co2(NHg)jp(NO.,)6-|-Co2(N02)g, 

 to a hot neutral solution of nitrate of luteocobalt. It may also be 

 formed by adding a solution of Co2(N02)g-|-6NaN02 in excess of sodic 

 nitrite to a solution of luteocobalt, there being in this case less danger 

 of the formation of other products than with the other cobaltamines. 

 1 find the formula of this salt to be 



lCo2(NIl3),2UCo,(N03),2f or Co,(:NH,\,(^0.;),+Co,(:^0,) 



c 



as the following analyses, made with three different preparations, 

 clearly show : — 



0-3312 gr. gave 0-2056 gr. SO,Co=z 23-78% cobalt. 

 0-3776 gr. gave 0-2369 gr. SO, Co = 23-89% cobalt. 

 0-1785 gr. gave 0-1115 gr. SO.Co = 23-78% cobalt. 



The formula requires 23-79% cobalt for the anhydrous salt. In 

 one preparation, however, I obtained a salt in which 



0-4291 lost 0-0087 gr. at 125° C. = 2-10. 



This would correspond to Sadtler's formula, which requires 1-78%, if 

 we consider a part of the water as hygroscopic, or that, as is more proba- 

 ble, there was a slight decomposition. In the dried salt, — 



0-4204 gr. gave 0-2643 gr. SO,Co = 23-93% cobalt. 



