Dr. Bostock on the Purification of Thames Water. 269 



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 transparent, and with- 

 out 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 sur- 

 face, which gradually subsided : 10,000 grains left by evapo- 

 ration a saline crust of a light brown colour, which, after being 

 thoroughly dried, weighed 7-6 grains. By the appi-opriate 

 tests, the water was found to contain lime, sulphuric acid, mu- 

 riatic 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 : 



grs. grs. 



Carbonate of lime ... 4.20 ... \.55'\ Salts contained in the 

 Sulphate of ditto 66... .12 { Lambeth water, which 



Muriate of soda ...\ ^ 2^ v,^^^ ^""^''■^^''^'^ ^^ ^'^^ 



Muriate of magnesia j *" ' "" " ^ j^most impure of the 



I specimens formerly ex- 



7.60 1.90J amined. 

 The result of this analysis shows, that although the water 

 has, by this depurating process, freed itself from the great 

 quantity of organic matter which it contained, and acquired a 

 state of apparent purity, which might render it sufficiently pro- 

 per for many purposes, yet that the quantity of saline matter 

 is increased as much as fourfold. The greatest proportionate 

 increase is in the muriates, which are very nearly twelve times 

 more in the purified water than in the Thames water in its or- 

 dinary state. The carbonate of lime is between two and three 

 times as abundant as before, and the sulphate of lime between 

 five and six times. I may remark, that this water, when ex- 

 amined in its foul state, gave very obvious indications of both 

 • Rcpore.p. 80-81. 



sulphur 



