34 REPORT— 186G. 



fore, the precipitant be put in over-night, the water will be ready for use in the 

 morning', and as time for the action to take place, and not quantity/ of icater is the con- 

 sideration, ten thousand gallons can as quickly be purified bj' this process as a 

 gallon. 



The chemical action is thus : — The lime which is in solution in the water as a 

 carbonate combines with the snlphm-ic acid of the sulphate, and forms sulphate of 

 lime. The liberated hydrate of alumina instantly attacks the organic matter, which 

 it renders insohible, and both rapidly descend to the bottom of the water, while the 

 carbonic acid gas which remains in the water imparts to it a sparkling freshness and 

 beauty. 



As the liberation of the hydrated alumina depends on the presence of carbonate 

 of lime in the water, and as its absence in terrestrial wiiters is a most rare occur- 

 rence, the applicabilitj^ of this precipitant for the purification of tei-restrial waters 

 may be said to be imiversal. 



In order to test the effect of the precipitant upon very dirty water, a gallon was 

 taken out of the Thames at half-tide, in the centre arch of London Bridge. Into 

 this water was put twenty di'ops of a standard solution of the precipitant. The 

 water was then allowed to stand eight hoiu's, when it was found that all the filth 

 had settled to the bottom, and the supernatant water was clear, sparkling, and 

 pleasant to drink. 



The author has therefore the greatest confidence in recommending the precipi- 

 tant for purifying the water contained in ships' tanks, and the waters taken from 

 tropical rivers and ponds, which in their natural state it is impossible to drink, in 

 consequence of the decaying organic matter contained therein, being a direct incen- 

 tive to cholera. If to such waters the precipitant be applied, they can be rendered 

 as perfectly salubrious as water taken from the deepest wells. The same effect can 

 be produced by the precipitant on tainted well-water, and the waters of stagnant 

 ponds which are left for the use of cattle in the comers of fields. 



For testing the superior salubrity of water which had been purified with the pre- 

 cipitant over the same nriter which had not been so purified, various experiments 

 were detailed. 



On the Oxidhhwi Action of Carbon. By Dr. Ce ace- Calvert, F.R.S. 



On Disinfection. By "William Ceookes, F.B.S. 



As an illustration of the want of general knowledge of the laws of disinfection, 

 and the evils resulting from the absence of combined action between the local self- 

 governing authorities, I may refer to what is being done in London in reference to 

 the present outbreak of cholera. The drainage of one thousand acres, saturated with 

 a powerfully cridizing disinfectant, mingles in the sewers with the'drainage from an- 

 other thousand acres, to which a powerfully deoxididmi agent has been liberally ap- 

 plied, the result being that an enormous amount of money is expended on various dis- 

 infectants and deodorizers, with veiy inadequate results ; and many valuable agents 

 may iiltimately fall into discredit from the want of a few simple discriminating rules 

 for their proper application. Disinfecting agents of great value are being used for 

 pui-poses for which they are totally imfit ; usefid but incompatible disinfectants 

 are recommended in the same paper of instructions ; and chemicals of the most 

 potent description ai'e given to ignorant persons without a word of warning as to 

 how they are to be applied. 



Disinfection is by no means so simple a process as is generally supposed. Che- 

 mists are aware that we cannot iise one substance with equal efficacy in all imagi- 

 nable cases. The process is one depending upon complicated chemical and physiolo- 

 gical actions ; and chemistry has placed at our disposal several substances which are 

 applicable to various requirements of the case ; but to pin one's faith to one agent 

 only, be it carbolic acid, chloride of lime, Condy's fluid, or McDougall's powder, is 

 to limit one's powers of disinfection in a very unwise degree ; whilst to recommend 

 all these things without discriniinatiug in Avhat cases they are severally to be used, 

 is like sending a sick man to a druggist's shop, telling him neither what special 

 drug to take, nor how much for a dose. 



