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IOWA ACADEMY OF SCIENCES. 



remainder, being relatively much longer. It therefore 

 seemed probable that a mixture was present. The attempt 

 was then made to recrystallize the salt. It was not possi- 

 ble to obtain it a second time until a large quantity of a 

 solution of the mixture 2NH4Br, Zn Br, was added. The 

 salt readily crystallized out of this mixture, but again in 

 both the longer and shorter crystals. The longer crystals 

 were now separated mechanically from the shorter and 

 analyzed. 



Calculated for Found Found 



3NH4Br, ZnBra- Longer Crystals. Shorter Crystals. 



Zn. 



12.6 



12.8 



12.5 



To determine whether the salt contained water of crys- 

 tallization 3.4428 grams were heated for four hours in an 

 air bath at 130". The loss was 0.9 per cent. The salt was 

 then further heated for four hours at 160^ when a slight 

 decomposition took place. The total loss in weight 

 amounted to only 1 per cent. It was therefore concluded 

 that the salt contained no water of crystallization, the 

 slight loss of weight observed being due to water which 

 could not be removed by drying paper on account of the 

 hygroscopic nature of the salt. 



The bromine in the salt was then determined by two 

 analyses and found to be 77.24 per cejit. The bromine cal- 

 culated for 3NH4Br, ZnBr^ is 77.01 per cent. 



A standard solution of the salt was prepared by determin- 

 ing the zinc in a measured volume of the mother solution. 



Conductivity of 3NH^Br, ZnBr„ {519.37). 



