288 
DU. BOSTOCK ON THE PURIFICATION OF THAMES WATER. 
doubt, they owed their buoyancy ; after some time the masses again subsided, 
leaving the fluid almost totally free from any visible extraneous matter. The 
quantity of gas discharged was inconsiderable, so that it was difficult to obtain 
any of it for examination. It seemed to be principally composed of carbonic 
acid, containing a little sulphuretted, and perhaps carburetted, hydrogen gas. 
When the process of depuration appeared to be complete, the water was 
filtered through paper, and was then subjected to the same mode of analysis 
which was employed on the former occasion*. It was now perfectly trans- 
parent, and without taste or odour, but still retaining a slight brown tinge. 
It sparkled when agitated or poured from one vessel to another, and by boiling 
a quantity of gas was disengaged from it : at the same time a thin film of 
carbonate of lime formed on the surface, which gradually subsided : 10,000 
grains left by evaporation a saline crust, of a light brown colour, which, after 
being thoroughly dried, weighed 7-6 grains. By the appropriate tests, the water 
was found to contain lime, sulphuric acid, muriatic acid, and magnesia. There 
was a trace of alumine and an indication of potash ; but no ammonia, sulphur, 
or iron could be detected. The lime, the magnesia, and the sulphuric and 
muriatic acids were all of them obviously in much greater quantity than in 
the specimens of the Thames water previously examined. If we suppose the 
sulphuric acid to be combined with a part of the lime, and the remainder of 
the lime to be in the state of carbonate, and that a part of the muriatic acid 
is combined with the magnesia and the remainder with soda, as was conceived 
to be the case in the Thames water generally, the respective quantities of these 
salts in 10,000 grains will be as follows : 
Carbonate of lime 
grs. 
4.20 
grs. 
1.55 1 
Sulphate of ditto 
.66 
.12 
Muriate of soda • • • I 
2.74 
.23 
Muriate of magnesia/ 
7-60 1.90 
Salts contained in the Lambeth 
water, which was considered as 
the most impure of the specimens 
formerly examined. 
The result of this analysis shows, that although the water has, by this depu- 
rating process, freed itself from the great quantity of organic matter which it 
* Report, p. 80 — 81 . 
