OF WATER FOR ORGANIC MATTER. 79 



there is a great deal, the ash melts readily. By white is 

 meant white as soon as it is incinerated. 



^' These acid nitrous waters contain phosphates generally. 

 Phosphate of lime, or even alumina and iron, may be pre- 

 cipitated from them by ammonia, if they are direct from 

 animal matter, and have not passed through porous matter 

 sufficient to deprive them of some of the less soluble 

 substances. 



" There are many interesting questions to be asked re- 

 garding nitrates. I am inclined to think that their 

 presence shows that the most dangerous state of the or- 

 ganic matter is past. When they appear in any solution, 

 the chief escape of putrid gas seems to have ceased ; the 

 water may, however, be still dangerous to use, and of 

 course i%revolting to the imagination. It will be well to 

 examine how far these suspicions are correct. When 

 complete nitrification has occurred, all that class of evils 

 arising from organic matter direct are prevented. 



" This paper was written for a special purpose, and does 

 not pretend to say all that may be said regarding organic 

 matter in water. As to the purification, there are many 

 points to be observed. It has been generally held that 

 nitric acid is the ultimate form which nitrogenous sub- 

 stances of organic origin assumes ; but we must remember 

 that plants have the power of decomposing nitrates, and 

 of using the nitrogen for their own purposes. There are 

 conditions, therefore, in which the organic matter may 

 be entirely removed from water ; and when we remember 

 how readily soils absorb phosphates and potash, we easily 

 see why common salt should chiefly be left. The oxygen 

 of the nitrates may even be used for the purification of 

 water, whilst the earthy salts and phosphoric acid are pre- 

 cipitated. This operation of decomposing the nitrates 

 seems to be the final one which is at hand for purifying 

 water, and probably explains the marvellous results we 



