Mr King on the Estimation of Colour in Water. 27 



and definitely stated. To enable me to do this, I elaborated 

 a process for the estimation of colour in water, which I will 

 now have the pleasure of describing to the Society, and 

 which, I may add, has lately been employed both by myself 

 and others, and has been found in every way satisfactory. 



The process, which is extremely simple, consists in adding 

 to a known quantity of pure distilled water contained in a 

 glass tube, an aqueous solution of caramel, of a certain 

 strength, from a burette, until the tint communicated to the 

 distilled water is found to equal that of the water under 

 examination. 



The tubes I employ are made of glass as free from colour 

 as possible; they should be 15 inches long, and of such 

 diameter that when filled to within 3 inches of the top, they 

 will contain 8 ounces of water exactly. 



Preparing the standard solution of caramel is the only part 

 of the operation attended with any difficulty. It is done by 

 adding caramel to distilled water until the proper depth of 

 tint has been attained. The depth of colour wMch it should 

 possess is ascertained as follows : To 8 ounces of 'pure, water, 

 perfectly free from ammonia, contained in a glass tube, and 

 forming a column 12 inches long, add 10 grains by volume of 

 solution of ammonium chloride, containing 3*17 grains of the 

 salt in 10,000 grains of water (or O'OOOl grain of ammonia in 

 1 grain of solution). To this mixture, after proper agitation, 

 add 25 grains by volume of Nessler's solution, of the usual 

 strength ; aUow this, after mixing, to repose for 10 minutes, 

 at a temperature of 60° F., when the colour produced will 

 equal 30° degrees on my scale. That is, 300 grains by volume, 

 or 30° (a degree being equal to 10 gTains by volume) of 

 caramel solution, if of proper strength, will produce exactly 

 the same depth of colour when added to the same amount 

 of distilled water (8 ounces) in a column 12 inches long. 



The caramel solution, which I should state can be kept 

 unchanged for a considerable length of time, being thus pre- 

 pared, all that is necessary to do to estimate the colour of a 

 water, is to fill two tubes, of the dimensions stated above, to 

 within 3 inches of the top, one with distiUed water, and the 

 other with the water to be tested ; and having placed them 



