1866.] with (he supply of water to Calcutta. 225 



product is distilled over and emptied into a tube graduated into 100 

 divisions of 10 fluid grains each, the bottles washed out with distilled 

 water and added to the tube to make up 100 measures of liquid which 

 is to be thoroughly mixed together. Two wide mouthed bottles or jars 

 of as nearly the same size as possible are provided, into each of which 

 25 fluid grains of the Hydrarg-Iodide solution is introduced with 

 some distilled water. Then into one of these an aliquot part of the 

 distilled liquid is poured, say ^ or J-, so as to produce a distinct colour, 

 and the bottle is filled up with water. Another similarly graduated 

 tube or burette has been prepared ready filled with the standard 

 solution of muriate of ammonia, and this is carefully added to the 

 second bottle, until the colour produced is as exactly as possible of the 

 same shade as that of the first, both bottles being of course made equally 

 full. The quantity added is then noted, and then calculated on the 

 whole. Thus : suppose 74 fluid grains of the standard solution of 

 muriate of ammonia has been required, this is equal to 74 X .0001 

 grains or .0074 grains ammonia. If 25 measures of the distilled liquor 

 has been used for trial, this is Jth of it, consequently the whole contains 

 .0074 X 4 = .0296 grains ammonia, and as this was from 10,000 

 fluid grains of water, by consequence the standard quantity of 100,000 

 fluid grains water contains .296 grains ammonia. 



The process requires great care, that there be no accidental 

 admixture of ammonia. The vessels must be scrupulously clean, the 

 distilled water and the lime used must be carefully examined to make 

 sure that they contain no ammonia. The plan of measuring the 

 distillate enables the operator to repeat the trial in case of accident 

 or uncertainty. It is better to work with rather weak colours, as the 

 eye can better detect differences of shade : .0074 grains ammonia is 

 too much for a 2000 grain bottle : any size of bottle may be used, 

 provided the two bottles be as exactly as possible alike in size, shape 

 and capacity. 



