2T4 § 141. BEVERAGES. 



another, is the source of the largest part of the hardness 

 of water, add a little hydrochloric acid to 100-500 c.c, 

 heat the mixture, and precipitate and determine lime with 

 the aid of ammonic oxalate, in the usual manner (§ 49, «). 



Or, by a more speedy though somewhat less accurate 

 method, to 100 c.c. of the water in a 300 c.c. flask, add 

 25 c.c, or, if the water is very hard, 50 c.c. of a ^ \^^ atomic 

 solution of oxalic acid, then add ammonia until the 

 reaction of the liquid is faintly alkaline, and heat the 

 mixture until it boils. 



After the liquid has cooled, add distilled water up to 

 the 300 c.c. mark, mix the whole well together, filter the 

 liquid through an unmoistened filter into a dry glass, 

 putting the first portions of the filtrate on the filter again, 

 if turbid, as is often the case. To 200 c.c. of the clear 

 filtrate, in a capacious flask, add 10 c.c. of concentrated 

 'sulphuric acid, heat the solution to 50-60° C, and deter- 

 mine the excess of oxalic acid in it with the aid of the 

 standard peraianganic solution (§ 69). By multiply- 

 ing the number of cubic centimetres of the standard 

 solution used by 1.5, the amount that would have been 

 required for the whole solution is obtained. Each cubic 

 centimetre of the solution of oxalic acid that did not 

 require to be decomposed by the permanganate, was 

 engaged in the precipitated calcic oxalate, and corre- 

 sponds to 0.0028. grm. of lime. 



(/. Hardncssof the Water.— 1. Clar/c's method. This, 

 though a convenient method of determining the hardness 

 of Avater, does not give highly accurate results ; it is, 

 however, generally used. 



The scale of hardness is expressed by the number of 

 milligrammes of lime in 100,000 mgrs., or 100 grms. of 

 water, that are required to produce the different degrees 

 of hardness, and this hardness is estimated by the amount 

 of soap precipitated from a standard solution of the 

 same. 



