30 PROCEEDINGS OF THE AMERICAN ACADEMY 



Calculated. Found. 



Co^P.Oia, 56-95 57-09 (Mean.) 



lONHg-fGOH^+O, 43-05 42-91 



100-00 100-00 



The formula requires 43-57 f;^ ^fia- Found 43-37%. The analj'sis 

 was made by fusing the salt with CO.jKNa, and precipitating as 

 ammoiiio-magnesic phosphate. Iodide of luteocobalt gives the same 

 salt, and does not yield an iodo-pyrophosphate Lc.P^O-.Ig as might 

 perhaps have been expected. 



Sulphate of Thallium and Luteocobalt. — "When a solution of thal- 

 lous sulphate containing free sulphuric acid is oxidized by potassic 

 hypermanganate, a dark brown precipitate is formed which readily 

 rcdissolves on the application of heat. The clear solution produces in 

 a solution of sulphate of luteocobalt, after a few minutes, a beautiful 

 crystalline precipitate of yellow talcose scales which have a peculiar 

 silky lustre. These crystals are decomposed by washing even with 

 cold water, a brown powder of thallic hydrate T1(0H)3 being formed. 

 The decomposition may be prevented by adding sulphuric acid to the 

 water. Of this salt : — 



0-5079 gr. gave 0-3169 gr. = 62-39% sulphates of cobalt and thal- 

 lium. 

 0-7421 gr. gave 0-6557 gr. SO,Ba = 36-40% SO,. 



In the last analysis, the thallium was first reduced in a solution con- 

 taining free chlorhydric acid by metallic magnesium, as zinc did not effect 

 a reduction even after long boiling. The precipitated spongy thal- 

 lium dissolved completely in the excess of free chlorhydric acid. The 

 formula of the salt is Co2(NH3),2(SO,),+Tl2.0.(Soi2+50H2, which 

 requires 36-49% SO, and 61-81% of the mixed sulphates, 2.SO,Co-(- 



so;n,. 



I did not succeed in obtaining analogous salts with the sulphates of 

 roseocobalt, xanthocobalt, or croceocobalt. It is remarkable that the 

 thallic sulphate in this salt is basic. I verified the analysis by a 

 second determination of SO,, made by decomposing the salt with hot 

 water, filtering off the thallic hydrate formed, and determining the 

 SO, in the filtrate by baric chloride. The analysis gave 3G-11%. 



Dichromate. — Potassic dichromate precipitates luteocobalt from 

 concentrated solutions of the nitrate in beautiful orange needles, which 

 may be redissolved and recrystallized without decomposition. The 

 salt dissolves rather easily in hot water, but dificrent preparations 



