OP ARTS AND SCIENCES. 29 



SO tliat the salt is identical with that described by Genth and myself 

 in the first part of this paper. When platinic chloride is digested with 

 neutral oxalate of luteocobalt, the salt ehantfes its form and color in so 

 marked a degree as to leave no reasonable doubt of the formation of a 

 new salt. On attempting, however, to purify this salt l»y solution in 

 boiling water and recrystallization, I found that decomposition at 

 once commenced, carbonic dioxyd being given off in abundance. 

 There can hardly be a doubt, I tliink, tiiat the salt, Co2(NI-Ig),2(C20j2 

 Cl.,-|-PtCl^, is at first formed, and subsequently decomposed. Oxa- 

 late of luteocobalt dissolves in hot oxalic acid, and yields a pale buff 

 felted mass of crystals of an acid oxalate. 



Pyrophosphate. — When sodic pyrophosphate is added to a solution 

 of luteocobalt, a beautiful crystalline precipitate is formed in talcose 

 scales with a high lustre, remarkably insoluble in water. Braun, who 

 first studied this salt, assigns to it the formula, — 



3 ( Co, ( N H,),03) +5 P2O,+40OH, 



(old style) and suggests that it may be a double salt with the 

 formula, — 



2(Co2(NH3)A-"PO,+80H)+Co2(NH3)P3.3PO,+240H, 



in which case it would contain both orthophosphoric and metaphos- 

 phoric oxides. My analyses have led me to the much simpler for- 

 mula, — 



Co,(NH,)^2.(PA334-60H2, 



the constitution of the salt being perfectly analogous to that of the 

 pyrophosphate of purpureocobalt already described. The salt analyzed 

 was precipitated from a hot solution of chloride of luteocobalt by a 

 solution of sodic pyrophosphate, well washed with cold water, and 

 dried in vacuo over sulphuric acid. Of the crystals, 



0-8178 gr. gave 0-4692 gr. by ignition = 57-30% Co,P,0,2. 

 0-8174 gr. gave 0-4651 gr. by ignition = 56-89% CV.P^O,.,. 

 0-5879 gr. gave 0-0693 gr. water heated up to 120° C. until the weight 



was constant = 11-78%. 

 0-7515 gr. gave 0-4359 gr. P,,0.Mg2= 43-37% P.O^g. 



The water given off up to 120° C. corresponds to five atoms, the cal- 

 culated percentage being 11-81. The last atom of water is retained 

 at 140^ C. 



