580 MINERAL SPRING AT RIETFONTEIN. 



Total Solids. — 250 c.c. of water of 15.9° were evaporated 

 and dried at 140° C, yielding a residue of 0.5647 grams, so that 

 100,000 c.c. of water of 4° contain 228.1121 grams of dissolved 

 solid constituents. 



Determination of the Anions. 



N 



Chlorine. — 100 c.c. of water of 20° C. require 36.725 c.c. — 



10 

 silver nitrate (mean of two determinations): hence 100,000 c.c. 

 of water of 20° C. contain 130.2269 grams of chlorine, and 

 100,000 c.c. of water of 4° contain 130.4578 grams of chlorine. 



Silica. — For the determination of silica, 3 litres of water 

 were evaporated to dryness ; the residue was digested with a 

 little hydrochloric acid, dissolved and filtered. The filtrate was 

 evaporated to dryness, and the above process repeated. The 

 residues, consisting of silica, with a trace of barium sulphate, 

 were dried, ignited, weighed, and treated with hydrofluoric acid. 

 The loss in weight after treatment with hydrofluoric acid repre- 

 sents the weight of the silica. The' values ol)tained from three 

 sets of determinations were as follows : — 



1. 100.000 c.c. of water of 4° contain 2.2629 grams of 

 SiC,. 



2. 100,000 c.c. of water of 4° contain 2.0199 gi'ams of 

 SiOo. 



3. 100,000 c.c. of water of 4° contain 2.2746 grams of 

 SiU,". 



Mean value 2.1858 grams SiO^. 



The silica is probably in solution as such. Hence the values 



// 

 are not worked out for SiCJ, ions. 



II 



Sulphuric Acid. (SO^j. — The filtrates from the above silica 

 determinations were used, and gave a mean value of o. 1766 of a 

 gram, to which is to be added the SO^ from the barium sulphate 

 precipitated with the silica, namely, 0.0516 of a gram, giving a 

 total of 0.2282 of a gram of SO4 per 100,000 c.c. water of 4°. 

 water of 4°. 



Alkalinity {HCO3'). — 100 c.c. of water at 15 -9° were neu- 

 " ■ N 

 tralised by i .53 c.c. — sulphuric acid (indicator methyl-orange) : 



50 

 hence 100 c.c. of water of 15.9° contain (5.001867 of a gram of 

 HCO:>, or 100,000 c.c. of water of 4° contain 1.86889 grams of 

 HCO;^. After the water had been standing for some time the 

 values for the alkalinity were much lower, a portion of the 

 soluble bicarbonates having been precipitated as carbonates. 



Nitric Acid (NO/). — Determined by reduction with zinc- 

 copper couple, distillation, and nesslerisation. It was found 

 that there was 0.00037943 of a gram of NO, in a litre of average 



