582 DR. URE ON THE MOIRA BRINE SPRING. 



By a skilful application of analytical resources, differences ten times smaller than 

 any represented by these numbers may be certainly appreciated in practice ; that is, 

 the result may be found within one part in a hundred. 



If 10 grains of the mixed salts be used for analysis by nitrate of silver, the following 

 arithmetical rule will be found sufficiently accurate. From the number 24*46 deduct 

 the weight of the silver precipitate, (perfectly dry of course,) and divide the remainder 

 by 0*6 ; the quotient will denote the proportion of bromide of sodium present in the 

 10 grains of the mixed salts. Thus, supposing that 22*9 grains of silver precipitate 

 have been obtained from 10 grains of a mixed chloride and bromide of sodium, the 

 difference between 24*46 and 22*90 is 2*46, which, divided by 0*6, gives for a quotient 

 the number 4*1, indicating four grains and one tenth of a grain of bromide of 

 sodium. According to Berzelius, bromide of sodium has for its prime equivalent 

 the number 101*7, hydrogen being unity, and consists of 78'39 bromine + 23*31 so- 

 dium. 



I have been in the practice of solving many problems in analytical chemistry by 

 the application of an arithmetical process analogous to the one above stated. 



The chloride and bromide of silver are both soluble in water of ammonia, and can- 

 not therefore be separated by this agent. 



The best experimental mode of effecting the complete separation of bromine and 

 chlorine in analysis may possibly be by converting the mixture of those two elements 

 into perchloride and perbromide of mercury, and decomposing the perchloride by 

 sulphuric acid. The perbromide is said to resist this powerful agent ; with what 

 truth I have not ascertained. Red oxide of mercury dissolves when agitated along 

 with water in the ethereous solution of bromine and chlorine, and affords a colourless 

 solution. 



