OP WATER FOR ORGANIC MATTER. 75 



Let US take another case. 



When heavy rains drove the impure water forward, the 

 chameleon gave the following : — 



Oxygen in Grains per Gallon required for the decomposed 

 and decomposing Matter. 



0*992 i*io6 



0*284 1*134 



0*638 1*276 



0*709 1*347 

 0*992 



III such a case the ordinary analysis gave 



Volatile matter. Fixed matter. 

 4*20 20*72 



4*48 21*21 



7*14 26*39 



6*o2 34*02 



4*27 28*28 



4*69 32*27 



These latter do not at all show the fine distinctions 

 made by the permanganate, which agrees entirely with 

 our senses, and may be used instead of them for putrid 

 substances. 



The permanganate must be used with consideration, 

 like all other chemical tests. We must be careful that 

 there are no lower metallic oxides in the water, which will 

 remove the colour as suddenly as the sulphuretted hy- 

 drogen from putrid matter. Much has been said against 

 the permanganate ; but nothing even pretends to do what 

 it does. Those who neglect it, leave out the putrid matter 

 or drive it off in boiling. 



Nitrites decompose chameleon instantly. They are the 

 result of the oxidation of azotized matter, and must be 

 estimated. 



" The decomposition of the chameleon may be caused by 

 the organic matter present, or by nitrites &c. The presence 

 of nitrites or nitrous acid will show if the organic matter 

 is only recently oxidized. 



" Generally there may be found organic matter and 



