CONDITIONS OF LIGHT, ETC. 



S£°£ ^ii^ ^2";/^ ^^^°' ^ ^^^ ^ ^'° ^ ^^ (HCO3) 2 



' o/lime ) ( andiuL'ur ) (Structural formula'^ (Condensed /ormula\ 



or MgCOg + H2CO3 = MgCOs + CO2 + H2O = Mg(HC03)2 



/ Carliimiite o/\ I Carbon dioxide\ t c-. ^ , j- , \ I ^ , , v 



V magnesia ) \ and ivater ) \btructural formula^ (Condensed formula^ 



The hardness produced by these causes is called temporary because it can 

 be removed by boiling the water, the bicarbonates being thereby changed 

 into the original simple carbonates by driving off the carbonic acid gas 

 and precipitating the carbonates in insoluble form: — 

 Ca (H 003)2 = CaCOs + H2O + CO2 



IBicarhonate\ I Carbo7iate\ I tl/„,.^ I Carbon\ 



\ o/time ) \ of lime ) (»'<""- j \dio^ide) 



The sulphates, nitrates and chlorates which cause permanent hardness are 

 not affected by boiling and are retained by the water. 



Water Analyses. Sorne years past the author had occasion to 

 make a number of analyses of Schuylkill and Croton river waters for 

 manufacturing purposes, and collected considerable data which is of 

 interest. 



For drinking and manufacturing purposes the analytical deter- 

 minations are usually ten in number, and these are, in their respective 

 order, Total .Solids, Mineral matter. Organic and Volatile matter, Organic 

 Carbon, Ammonia both free and albuminoid. Nitrogen, in any or all 

 the forms of nitrates and nitrites, combined nitrogen and organic nitro- 

 gen. Chlorine and Metallic salts; also the amount of Oxygen required to 

 oxidize the water, usually by the permanganate of potassium color test, the 

 degree of hardness, and a microscope examination. These are more than 

 are required for the examination of aquarium water. 



It is of interest to note that an analysis of the water of a balanced 

 aquarium, which had not been changed for eight months, made for Mr. 

 Mark Samuels by Prof. Leeds, should be of such remarkable purity. As 

 may be naturally supposed the aquarium water contained the greatest 

 proportion of solids, mineral matter, chlorine and the highest degree of 

 hardness, due to easy explained causes. Rain water is the lowest in all of 

 these constituents, while the very highest are Deep well and Spring waters. 

 In point of purity as to ammonia, the aquarium water is as low as many 

 of the city supply waters; and as to nitrogen, the proportion of nitrites is 

 lower than Schuylkill water and the nitrates but two-tenths higher. The 

 high percentage of chlorine is to be explained by the probable addition of 

 table salt, from time to time, in the aquarium, and from the animal waste. 



All natural waters are chemically impure, though they may be per- 

 fectly clear and free from suspended particles. They contain substances 

 in solution, due to water being a natural universal solvent, which more 

 than any other liquid dissolves and takes up solids, liquids and gaseous 



173 



