68, 69] Estimation of Chlorine 45 



factor will have to be used with it — that is to say, the number 

 of c.c. used in any operation will have to be multiplied by 

 a number or factor to tell us how many c.c. would have been 

 used had the solution been accurately decinormal. 



This must be calculated from the weight taken in the 

 following manner : 



Suppose the actual weight taken to have been 16*9545 

 grams. 



Now, 17 grams AgN0 3 are contained in 1000 c.c. — AgN0 3 , 



10 



1 gram „ is 



1000 



and 16-9545 grams AgN0 3 are „ ™°° x 163.5 45 ^ 



This fraction works out to 997*3. 



But 16-9545 grams AgNO a are contained in 1000 c.c. of our solution, 



N 

 .*. 1000 c.c. of our solution = 997*3 — AgNO a , 



or 1 c.c. ,, „ ='9973 



That is to say, if we multiply the number of c.c. of our 

 solution used in any operation by '9973, the product will be 

 the number of c.c. which would have been used had the solu- 

 tion been decinormal. Therefore '9973 is the factor for this 

 solution. 



68. Potassic Chromate Solution.— A 2 per cent, so- 

 lution of pure neutral potassic chromate is made. This should 

 be perfectly free from chlorine. It may be tested by adding a 

 drop of nitric acid to a small quantity, and then a drop of silver 

 nitrate solution. If it remains perfectly clear, chlorides are 

 absent. 



69. The Estimation. — Weigh out accurately about 

 1 gram of pure common salt (NaCl) into a small beaker; dis- 

 solve this in 50 c.c. of cold water, transfer into a 250-c.c. 



