H. L. Wells— Discussion of Triple Salts. 29 



Cs 3 BaAg (NO, ) 6 .2H 2 Cs 3 PbAg (NO, ) 6 .2H,0 



Cs 3 SrAg (N0 2 ) G .2H 2 K 8 PbAg (N0 2 ) 6 .2H 2 



It is to be observed that the compounds in the first 

 column contain the same metals as two of the triple thio- 

 cyanates, but the formulas do not correspond, nor was 

 the 3:1:1 ratio, which these nitrites show, found at all 

 among the triple thiocyanates. Triple nitrites appear to 

 be formed with particular facility, and a few others will 

 be mentioned here to show their types. 



The salt K 2 CaNi(N0 2 ) 6 was described by Erdmann, 8 

 and the analogous strontium and barium compounds are 

 known also. The compound K 2 NaCo"'(N0 2 ) 6 is well 

 known as the precipitate obtained in a qualitative test 

 for potassium, while the analogous salts (NH 4 ) 2 NaBi 

 (N0 2 ) 6 , Bb 2 NaBi(N0 2 ) 6 and Cs 2 NaBi(N0 2 ) 6 have been 

 described by Ball. 9 



A triple chloride described by BonsdorfT 10 a very long 

 time ago is worth mentioning on account of its irregular, 

 complex formula, K 6 CuHg 3 Cl 14 .2H 2 0. Its composition 

 was confirmed in this laboratory by H. F. Merriam, 11 who 

 prepared and partially analyzed it. 



Triple cyanides are known, such as the precipitate, 

 K 2 CaFe(CN) 6 .3H 2 0, obtained with potassium ferrocy- 

 anide in Baubigny's test for calcium. Of course this 

 may be called a double ferrocyanide. 



The following are examples of triple salts that occur 

 as minerals : 



Paclmolite, NaCaAlF 6 .H,0 

 Polvkalite, K,Ca,Mg(S0 4 ),.2H,0 

 Thaumasite, CaC0 3 .CaSi0 3 .CaS0 4 .15H,0 

 Sulphohalite, 2Na,S0 4 .NaCl.NaF. 

 Hanksite, 9Na 2 S0 4 .2Na 2 C0 3 .KCl 

 Kainite, K,SO,.MgS0 4 .MgCl,.6H,0 

 Northuptite, MgC0 3 .Na,C0 3 .NaCl. 



The first two of these show that fluorides and sulphates 

 are capable of forming triple salts, the next two are triple 



s J. prdkt. Chem., 97, 395. 



9 J. Chem. Soc, 87, 761; 95, 2126. To the cesium salt, which is obtained 

 as a precipitate in Ball's test for sodium, the formula Cs Na Bi 3 (NO 2 ) 30 was 

 ascribed, but the simpler formula, differing but slightly from it and analo- 

 gous to the others, appears preferable after a careful consideration of the 

 original description. 



10 Pogg. Ann., 33, 81, 1834. 



n Amer. Chem. Jour., 28, 256 (1902). 



