ON SOME DOUBLE COMPOUNDS OF NICKEL AND COBALT. 213 



Fig. 2.— Series B. 



The Konnan numbers indicate the different fractions of the conjugated salts. The co- 

 ordinate numbers show the percentage of NiO, and the abscissa; numbers the percentage 

 of CoO in the several fractions. 



It will be seen from these numbers that a regular replacement between 

 the nickel and cobalt oxides takes place, while the percentage amounts of 

 water, sulphuric anhydide, and potassium oxide remain the same. In the 

 several successive fractions we have a regular decrease of the quantity of 

 nickel with an increase in the quantity of cobalt, the amounts of both to- 

 gether, however, giving a practically constant number for each fraction. 



Taking the quantities of nickel and cobalt together, the formula given by 

 Vohl might express the relation thus (M"M")K 4 (S0 4 ) 4 ,12H 2 ; but to ex- 

 press the replacement we have found between the metals, a much higher 

 molecular formula is necessary — the one which admits of all the replace- 

 ments shown by the numbers we have obtained being 24 [M"M"K 4 (S0 4 ) 4 , 

 12H 2 0], and it is possible fractions containing a higher replacement of the 

 metals might be obtained requiring a still higher molecular formula ; in fact 

 the limits of replacement are only defined by the powers of analysis. 



There are certain further conclusions which may be drawn from the re- 



