t 837 J 



tinually stirred. K 2 CrO 4 gives a reddish brown precipitate 

 with 2 AgNOs, with the formation of Ag 2 GrD 4 . But this 

 is not permanent, .as the Cl present as NaCl as an impurity 

 in the Nitrate-solution, is immediately attacked by AgNo 3 , 

 or rather Ag 2 CrO 4 , to form AgCl. When sufficient of the 

 AgNQs solution has been used, all the Cl gets just used up. 

 This is indicated by the formation of a slightly permanent 

 reddish brown colour due to Ag 2 CrO 4 . 



(4) Lime is determined in the usual way: 100 c. c. of 

 the remainder of the Nitrate-solution is sucked up with a 

 pipette, placed in a clean beaker, heated nearly to boiling, 

 (NH 4 ) 2 C 2 O 4 and NH 4 HO are added in excess until all 

 precipitation ceases, and the liquid smells strongly ammonia- 

 cal. It is left covered up over-night in the Sand-bath, then 

 filtered through Swedish paper, washed, dried, gently ignited, 

 and weighed in the usual way. The weight of CaCO 3 deter- 

 mined is due to the amount of Calcium Sulphate present in 

 7 grams of the sample of the Nitrate (t. e. 100 c. c. of the 

 solution). 



(5) Sulphur Trioxide. 100 c. c. of the original 500 c. c. 

 of the Nitrate-solution should be taken and made into 

 300 c. c. with distilled water ; boiled ; precipitated with 

 Barium chloride. Nitric acid is also added to intensify the 

 action. The precipitate is allowed to settle in sand-bath. 

 It is next day filtered, dried, ignited and weighed in the 

 usual way, and the amount of BaSO 4 determined, taken in 

 connection with the amount of Lime previously determined, 

 gives the amount of CaSO 4 present as impurity. 



i ,4 1 4. The Standard Silver Nitrate-solution. For estima- 

 tion of Chlorine (or its equivalent of NaCl) in substances 

 analysed, it is necessary to have a standard solution of silver 

 nitrate always ready. The Decinormal solution is in general 

 use. It is made by dissolving 16-97 grammes of pure silver 

 nitrate in 1000 c. c. of distilled water. The solution must be 

 neutral. Now the molecular weight of AgNO 3 is 1697, 



