182 Proceedings of the Boycil Physical Society. 



nitrogen wliicli is present in a water is of animal or of vege- 

 table origin, has been taken exception to, because it does not 

 show whether the organic nitrogen is in a decomposing state ; 

 this objection is quite untenable, because if the nitrogen is 

 undergoing oxidation, there will be present in the water the 

 products of the change, and these will exist either as a nitro- 

 compound or as ammonia. 



There are a few, but so far as is known very few, compounds 

 of nitrogen which do not yield the whole of their nitrogen to 

 potassium permanganate, and there are one or two that yield 

 a distillate which, on being nesslerised, gives a white preci- 

 pitate instead of a brown colour ; but this reaction, instead of 

 condemning the process, in my opinion recommends it ; be- 

 cause the abnormal reaction suggests at once that there is 

 present something even more objectionable than sewage con- 

 tamination. I have experienced such a case, and, so far as I 

 am aware, the reaction which I somewhat accidentally dis- 

 covered has not before been noted, wherein a water supply 

 had been polluted with carbolic acid ; the distillate from this 

 water was slightly opalescent, and on being nesslerised 

 yielded a white precipitate which, of course, masked the am- 

 monia reaction ; but at the same time, this very unusual occur- 

 •rence necessitated an inquiry as to the cause, with the result, 

 as I have just indicated, that carbolic acid was ascertained to 

 be present. 



Another. objection which has been made to the ammonia 

 process is, that the distillates, after being nesslerised, are 

 liable to be affected by ammonia in the atmosphere, and in 

 consequence thereof too high results obtained ; this objection 

 is, I am perfectly satisfied, quite groundless ; for if the 

 merest trace of ammonia be introduced after the nessler solu- 

 tion has been added, the whole contents of the nesslerising 

 tube become almost instantly opalescent ; indeed, I may say 

 I have had nesslerised distillates standing in an atmosphere 

 whicli was by no means free from ammonia for sixteen hours, 

 without any notable change in the depth of colour taking 

 place. Just a few words regarding this opalescence, and I 

 have done. In preparing standard solutions with which to 

 compare distillates obtained from this ammonia process, 



