88 H. L. Wheeler — Double Halides of 



The purity of the nitrate as a condition of success is to be 

 emphasized. One specimen tried, which contained nitrite, was 

 absolutely worthless with the foregoing treatment. 



To see what CuS0 4 would do under circumstances similar 

 to those in which the nitrate was studied, a saturated solution 

 of the sulphate was rendered neutral by the copper hydrate 

 precipitated on addition of ammonia. NH 4 C1 was added until 

 the deposit was as bright and lustrous as that formed in an 

 acid sulphate solution. 



Three such experiments yielded 



Eq. = 3295 xlO-f 

 Eq. = 3293 XTO" 7 

 Eq. = 3294 XI0- 7 



Two other experiments in circuit with the nitrate showed 





Sulphate. 



Nitrate. 





gms. 



gms. 



Copper deposited 



0-4722 



04719 



do. do. 



0-5671 



0-5667 



These values tend to confirm the result obtained from the 

 nitrate ; at least they do not contradict it. 



In conclusion I wish to express my thanks to Professor A. 

 W. Wright, under whose direction the preceding investigation 

 was made, for his many kind and helpful suggestions. 



Sloane Physical Laboratory, June 1st, 1893. 



Art. XII. — On the Double Ilalides of Arsenic with Caesium 

 and Rubidium / and on some Compounds of Arsenious 

 Oxide with the Ilalides of Ccesium, Rubidium and Potas- 

 sium ; by H. L. Wheeler. 



ISTo compounds of arsenious halides, with alkaline halides, 

 have been definitely described. Nickles* in his work on the 

 bromides and iodides of arsenic, antimony and bismuth, states 

 that these salts combine with alkaline bromides and iodides 

 respectively, but in the case of arsenic he gives no analyses of 

 the compounds which he obtained and he does not describe 

 the methods that he used in preparing them. He does not 

 even state with what alkaline halides he performed his experi- 

 ments. Emmetf, Harms:];, Schiff and Sestini§ have described 



*Compt. Rend., xlviii, 839; Journ. Pharm., Ill, xli, 142: Rep. chim. pure, i, 

 366. 



f This Journal, I, xviii, 68. % Ann. Chem. Pharm., xci, 371. 



§ Ibid., 228, 12. 



