EXAJMINATION OP WATER FOR ORGANIC MATTER. 37 



II. On the Examination of Water for Organic Matter. 

 By R. Angus Smith, Ph.D., F.R.S., &c. 



Read December 24th, 1867. 



In 1865 I received a request to write on the organic 

 matter of water. I wrote a memoir, which was, without 

 being published, extensively circulated among officers of 

 health, especially in India. 



I there made a division which was entirely new to che- 

 mists. The substance styled " organic matter,^^ instead of 

 being given as one to which little or no meaning was 

 attached, was considered as existing chemically under at 

 least seven different headings, not forgetting the nume- 

 rous organized forms which it might assume. These 

 divisions were — 



1st. The organic matter decomposed, or putrid. 



2nd. Organic matter readily decomposed, and probably 

 ready to become putrid. 



3rd. Organic matter slow to decompose. 



4th. Recent organic matter. 



5th. Old organic matter. 



6th. Vegetable organic matter. 



7th. Animal organic matter. 



The first was known by the gases which instantly de- 

 composed permanganate. 



The use of the permanganate of potash, recommended 

 by Forchhammer for ascertaining the organic matter of 

 water, has been tried and admired by some, and found 

 entirely wanting by others. 



I endeavoured to show, in the memoir alluded to, and 

 in a subsequent paper, how far that salt could be trusted, 

 quite certain of its value for ascertaining bodies of the 

 first and second classes, but having no experience of my 



