1898.] of Copper and Sodium. 235 



Cuprous Sodium thiosulphate Cupric Sulphide : — 



(1) Cu 2 S,0 3 Na 2 S 2 3 Cu S 4 H 2 (Lenz. A. 40, 99). 



(2) Cu a S 2 3 Na 2 S 2 3 2 Cu S (Kessel B. 11, 1585). 

 Cuprous Sodium thiosulphate Sodium Chloride : — 



3Cu 2 S 2 3 2Na 2 S 2 3 4 Na CI 8 H 2 (Siewert, Zeit. ges. 



Naturwiss. 26, 486). 

 Cuprous thiosulphate sodium dithionate : — 

 (J) Cu 2 S 2 3 4Na 2 S 2 0, 4H 2 (Vortmann). 

 (2) 2Cu 2 S 2 3 Na a S 2 4 2I^a 2 (Jochum). 



See Dictionary of Chemical Solubilities, Inorganic by A. M. 

 Comey, 1896, page 474, and Dnmmer's Handbook II, 2 pages, 688-89. 



The yellow salt to which Lenz and Siewert assigned the formula 

 Cu 2 S a 3 , Na 2 S 2 3 , Cu S, 4H 2 0, was found by Kessel to have the 

 above composition when prepared at 10°C, and to vary in composition 

 with variation of temperature. Kessel further noticed that the yellow 

 salt is obtained when the copper sulphate and sodium thiosulphate are 

 mixed in the proportion of one molecule of the former to two molecules 

 of the latter. He further says that the reaction takes place in two 

 stages. According to him the yellow salt is decomposed by cold strong 

 hydrochloric acid forming a white mass which contains neither free 

 sulphur nor copper chloride, is permanent when dry, but in contact with 

 moisture decomposes witli separation of copper sulphide and evolution 

 of sulphur dioxide. He is, however, of opinion that the sodium chloride 

 is present as an impurity having had nothing to do with the composi- 

 ti6n. 



Vortmann on the other hand, disagreeing with Kessel describes two 

 salts, one a greenish yellow salt Cu 2 S 2 3 Na 2 S 2 3 H 2 and the 

 other an intense citron yellow salt 3Cu 2 S 2 2 2Na 2 S 2 2 8H 2 0. The 

 former according to him is obtained in microscopic needles when saturated 

 solutions of copper sulphate and sodium thiosulphate are mixed together 

 in the proportion of one molecule of the former to two molecules 

 of the latter. When, however, the solutions are previously heated 

 to about 40°C and then mixed together, the temperature of the mixture 

 rises about 5° — 7° and the salt with the composition 3 Cu 2 S 2 3 2Na 2 S 2 3 

 8H 2 separates out, also in microscopic needles. The yellow salt is 

 unstable and decomposes thus — 3 Cu 2 S 2 3 2 Na 2 S 2 3 8H 2 = 3Cu 2 S 

 4 2Na 2 SO,+H 2 S0 4 + S 2 + 2S0 2 -r7H 2 0. 



The salt we are going to describe agrees in some respects with the 

 yellow salt described by Lenz and Siewert and confirmed by Kessel, as 

 also with that described by Vortmann. That there should be copper 

 sulphide present in a salt with such an intense yellow colour seemed to 

 ns strange. This led us to analyse the salt once a^ain. To start with, 



