96 63. BASES AND ACIDS WITH REAGENTS. 



18.7 c.c. of argentic nitrate were required, we learn by 

 the proportion, 



0.11 : 18.7 = 5.85 : 994.5, 



how much of the argentic solution that we liave made 

 would be required for the desired purpose; we must 

 therefore add 5.5 c.c. of distilled water to 994.5 c.c. of the 

 argentic solution, to make a litre of a solution that shall 

 be exactly equivalent to 5.85 grms. of sodic chloride, or 

 3.55 grms. of chlorine ; or, since it is more convenient to 

 measure out one litre of the solution, and add a small 

 quantity of water accurately measured with the pipette, 

 we may learn from the proj^ortion, 



994.5 : 4.5 = 1000 : x, 

 how much water will be required for one litre. 



Rej^jeat the test made with one portion of the salt with 

 two of the remaining three portions, keeping the first at 

 hand as a standard of comparison, substitute the mean of 

 the quantities of salt taken and of the three correspond- 

 ing results in the place of the first and second terms in 

 the first proportion given above, and make the standard 

 silver solution accordingly; then, in order to be sure that 

 the work has been correctly done, rinse the burette out 

 with a little of the solution last prepared, fill up to the 

 zero mark with this solution, and make a fourth trial with 

 the last weighed 2:)ortion of the sodic chloride. The num- 

 ber of cubic centimetres of the standard solution required, 

 multiplied by 0.00585, should give a product exactly equal 

 to the amount of salt taken. 



One cubic centimetre of this solution corresponds to 

 0.00355 grm. of chlorine. 



The solution in which chlorine is to be determined 

 with the aid of this standard solution must not be acid 

 in the slightest degree, but should be neutral, or at the 

 most very slightly alkaline. If strongly alkaline, it should 

 first be neutralized with nitric acid ; if acid, with sodic 



