CHEMISTllY. 215 



pouring the water on to the salt, and stirring up with a very deli- 

 cate and highly sensitive thermometer; the maximum decrease 

 of temperature took place within a minute after the mixing of 

 the sailt and water. Of a considerable number of salts experi- 

 mented upon, the sulphocyanide of j^otassium caused the great- 

 est decrease of temperature. When 150 parts of the salt'were 

 mixed with 100 parts of water, the temperature fell from 10.8° C. 

 to — 23.7° C, that is, through 3-4.5°. 



AVhen 133 parts of sulphocyanide of ammonium were mixed 

 wnth 100 parts of water, the temperature fell from 13.2° to — 18°, 

 or through 31.2°. 



When 60 parts of nitrate of ammonium were mixed with 100 

 parts of water, the temperature fell from 13. G° to — 13.6°, that is, 

 through 2Q.2°.—BudorJf. Bent. Ch. Ges., Berlin, 1869. 



Freezing Mixture. — If citric acid and crystallized carbonate of 

 sodium in powder be stirred together, the temperature falls from 

 -|- 60° F. to — 80° F. — Chem. News. 



PURIFYING WATER. 



The inhabitants of tlie towns and villages along the River 

 Maas are dependent upon its waters for domestic and drinking 

 pni-poses. The water is turbid, does not become clear on stand- 

 ing, and produces, in those not accustomed to its use, a diar- 

 j'hcEa, sometimes accompanied by dangerous symptoms. Anah- 

 sis fails to reveal the cause of this property. Dr. Gunning, of 

 Amsterdam, has found that perchloride of iron added to this 

 water (and the same applies to far more foul waters experi- 

 mented upon) renders it wholesome and even agreeable to use. 



To one litre of the water is added 0.032 gram of tiie dry salt 

 dissolved in pure water, and the liquid, after stirring, is allowed 

 to stand for 36 hours. On a large scale, a small quantity 

 of carbonate of sodium is subsequently added to neutralize any 

 free chlorhydric aeid. Comparative experiments have proved 

 that the application of this process is far superior to filtration, 

 even through animal charcoal. The result obtained with the 

 Maas water having been so eminently successful, the committee 

 has applied this method to the purifying of water, otherwise un- 

 drinkable, such as is met with in the smaller canals, brooks, and 

 wells containing surface water ; thus treated such waters become 

 available for use. 



The precipitate formed by the addition of perchloride of iron 

 and carbonate of sodium contains a large quantity of organic 

 matter. Analysis shows that the only addition to the inorganic 

 constituents of the water is one part of chloride of sodium to 

 40,000 pai'ts of water. — From the Report of the Netherlands Com- 

 mittee. — Chem. News. 



SEWAGE. 



The sewage water from Paris taken at the bridge near Asni- 

 eres contains one kilo, of solid matter to the cubic metre ; of 



