222 MINERAL WATERS, WELL-WATERS, ETC. 



with some starch paste containing iodide of potassium 

 and sulphuric acid. A small piece of bright zinc is 

 placed in the mixture which reduces the nitric acid 

 to nitrous, and gives the iodine reaction. 



VIII. The chlorine is precipitated by nitrate of 

 silver after acidifying the water with nitric acid ; the 

 precipitate is treated as in No. 1. 



IX. Bromine and iodine, present only in very 

 small quantity, can only be detected and estimated in 

 large quantities of water, or in the mother-liquid. 

 They are recognized as in Nos. 113 and 114. If 

 the quantity of iodine present is very small a few 

 drops of pure iodide of potassium and hydrochloric 

 acid are added to the water, and the amyl reaction made. 

 In order to concentrate the bromine, the water may be 

 evaporated to dryness, and all the bromide of sodium, 

 with but little chloride, extracted from the residue by 

 absolute alcohol. When the alcohol has been evapo- 

 rated or distilled oft) the residue is dissolved in water, 

 and a small quantity of nitrate of silver added, with 

 constant stirring, so that only about \ of the chlorine 

 may be precipitated as chloride of silver ; the precipi- 

 tate which contains all the bromine is weighed, and a 

 certain portion of it analyzed as in No. 114. 



X. The sulphuric acid is precipitated by chloride of 

 barium from the water slightly acidified with hydro- 

 chloric acid. 



XI. Potassa and soda. The water is evaporated to 

 about one-half, and mixed, without filtering, with ex- 

 cess of baryta- water ; the mixture is allowed to cool, 

 and carbonate of ammonia added ; in this way, the sul- 

 phuric acid, lime, and excess of baryta are precipitated. 

 The filtrate is acidified with hydrochloric acid, evapo- 

 rated to dryness, and the residue, which is a mixture 

 of chloride of sodium, chloride of potassium, and 

 chloride of magnesium, is then cautiously heated to 

 redness. The three metals are separated as in No. 11. 



