224 M. Gai/-Lussac on the Chloride of Lime. [Sept. 



into the jar. Make up the volume to exactly half a litre, and 

 stir it to render it perfectly homogeneous. Fill the tube (I) with 

 proof tincture up to 0°, and pour a portion of it, less than that 

 which you suppose will be discoloured by the chloride, into the 

 glass H, for instance, 5°. 



Take one measure of chloride in the small tube F, and make 

 it flow quickly into the proof tincture, by blowing into the tube, 

 agitating the mixture the whole time. If the tincture be com- 

 pletely discoloured, add quickly from the tube I, such a fur- 

 ther quantity as to give the liquid a slightly greenish colour ; 

 the quantity of proof tincture taken from the tube I, will be the 

 measure of the quality of the chloride, provided the second por- 

 tion added be not considerable, nor amount to three-tenths 

 of a degree. 



But if the second portion of proof tincture added to the chlo- 

 ride, exceed the quantity of three-tenths of a degree ; if, for in- 

 stance, it amount to T2°, the assay must be begun again. Fill, 

 the tube I with the tincture, and pour as much of it into the 

 glass H, as is equal to the quantity discoloured in the former 

 experiment, and some hundredths over. Then complete the 

 operation in the manner already described. The assay has not 

 attained the utmost precision it is capable of, till the proof tinc- 

 ture assumes the slightly greenish tint, immediately on the 

 chloride being added, without a fresh quantity being required. 



By these successive operations we approach as near as we 

 please to the true quality of the chloride ; nevertheless, I do 

 not think that we can in general be certain of it beyond ■ 3 l B -tk. 

 These operations may, perhaps, appear complicated, but I must 

 remark, that each of them may be executed in two or three 

 minutes ; that when we previously know pretty nearly the 

 quality of the chloride, two operations are sufficient, and that 

 in the curreut labours of a manufactory one assay will be 

 enough. Moreover, the object is to ascertain the quality of the 

 chloride, in order to fix its commercial value, and in that case 

 we must not be niggards either of our time or our pains. 



The same process is directly applicable to the assay of a so- 

 lution of chlorine in water; but it is better to begin by adding 

 a little powdered quick-lime to the liquid to convert it into chlo- 

 ride. 



The tube K, which forms part of the chlorometer, is intended 

 for assaying the chloride, by pouring the indigo quickly into 

 the chloride, For this operation the quantity of tincture re- 

 quired to saturate one measure of chloride must be previously 

 ascertained by the tube I. 



The assay is then begun again by putting into the tube K, a 

 quantity of tincture equal to that which has been discoloured, 

 and a small quantity over, which must be poured quickly into a 

 fresh measure of chloride ; as much tincture must then be added 



