Analysis of the Hot Springs at Bath. 359 



Exp. I. Exp. II. Mean. 

 Sulphate of barytes 36-6 grains SG'Q 36*7 



Carbonate of lime 1-7 do. 1-5 1*6 



Silica '3 do. '4 -35 



According to Dr. Gihbe?, a quart of the water affords 

 nearly 4 grains of silica when treated in the method I have 

 described. Thinking it probable that a portion of it might 

 be taken up by the action of the salts during their solution 

 in water, I tried whether any larger quantity could be ob- 

 tained by the following method : 



(£) A quart of the water was evaporated to dryness in a 

 platina crucible. The residuum was repeatedly treated with 

 nitric acid in a red heat ; the soluble parts were again dis- 

 solved by distilled water, and the portion insoluble in it, 

 when dried, weighed -4 of a grain. This agreeing exactly 

 with ihe last experiment, I shall consider as the quantify of 

 silica afforded by a quart of the water. This experiment 

 was several times repeated, with very little variation in the 

 weight of the result, but was sometimes evidently coloured 

 by oxide of iron, which was separated from the silica, and 

 its nature ascertained by the usual means. But, even when 

 employing apparently perfectly similar means, the oxide of 

 iron was not always to be obtained, — an effect attributable to 

 the decomposition of the nuiriate of soda by the nitric acid, 

 and to the power which muriatic acid possesses of carrying 

 Q^ oxide of iron ; but for th.e uncertainty of its action it is 

 not easy to account. 



To find the quantity of oxide of iron contained in the 

 water, the following means were employed : 



(F) To a quantity of the hot water infusion of galls was 

 added in the requisite proportion. The water measured 

 when cold 9,^- pints. The precipiiate obtained v.-as separated 

 by the filter, and dried :- — the precipitate and filter were then 

 burned together in a platina crucible, and the carbonaceous 

 matter of the filter, and that combined with the iron, were 

 got rid of by the application of a red heat. The residuum 

 was then treated with nitric acid, in order completely to 

 oxidise the iron: — it was then boiled with acetic acid to 

 Z 4 take 



