288 



DR. 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 diificult 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 trjms- 

 parent, and witliout 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 Tliames water generally, the respective quantities of these 

 salts in 10,000 grains will be as follows : 



Carbonate of lime . . . 

 Sulphate of ditto .... 

 Muriate of soda ... "1 

 Muriate of magnesia J 



grs. 



4.20 

 .66 



2.74 



7.6O 



grs. 



1.65 

 .12 



.23 



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. 



