Dr. E. J. Mills on certain Cobaltamines. 257 



^-Pentammoniochloride. — The conditions that the filtrate shall 

 be neutral are 



2CoCl 2 + 2 (CoCl 3 . 5NH 3 ) + (5 +n) H 2 ; 



which give these results, 



Co 4 O 5 . nW + 10 (NH 3 . HC1) . 



1*4847 grm. pentammoniochloride and 0*77454 grm.cobaltic 

 chloride* were boiled in an open beaker with 318*25 cubic cen- 

 tims. water for three quarters of an hour. The precipitate, 

 dried at 70°-80°, weighed 0*8199 grm. • 0*2705 grm. of it gave 

 0*01825 grm. water and 0*46675 grm. cobaltic sulphate. Hence 

 the composition of the precipitate was 



Found. 



t -* > Co 2 3 f. 3Co 2 3 .2H 2 0. 



Cobalt . . 66-37 \f 71*17 71*43 66-67 



Oxygen. . 26*88j\28-83 28*57 26*66 



Water . . 675 6*67 



100*00 100-00 100*00 100-00 



Also the amount of cobalt grm. 



due from the ammonio-chloride is . 0*3542 



„ „ chloride is .... 0*3547 



Total 0*7089 



found in the precipitate was . . . 0*5442 



The evolution of a small quantity of ammonia during ebulli- 

 tion was the only very noticeable feature in the reaction. Its 

 occurrence is evidently owing to the interference of the products 

 of decomposition with each other. The precipitation of dicobaltic 

 teroxide instead of tetracobaltic pentoxide was manifestly due to 

 atmospheric oxidation; and the numbers show that considerably 

 more than half of the cobaltic chloride was decomposed. The 

 discrepancy between the statement of Fremy and that of Gibbs 

 and Genth (see Sect. I.) probably finds its solution here, — it 

 being quite possible that the former chemist applied heat for a 

 considerable time to the liquid with which he worked, and thereby 

 obtained the sesquioxide ; while the latter, having dealt with a 

 gentler reaction, may with equal likelihood have obtained the 

 magnetic oxide. 



I have repeated the above experiment in a closed vessel. 



0*8094 grm. pentammoniochloride, 0*4225 grm. cobaltic 

 chloride J, and 64*5 cubic centims. water were heated together 



* The excess is intentional: 0*77334 grm. is the theoretically equal 

 amount. 



f 2Co 2 3 = Co 4 9 .0. 



X 0*4216 grm. is the calculated quantity. 



