2.20 



REPORT — 1876. 



It appears that during the months of June, July, August, and September 

 little or no nitrogen as nitrates or nitrites was found in the effluent water ; 

 and from this it might hastily he concluded th'at for some reason or another 

 the usual amount of oxidation had not gone on in the soil ; hut the fact turns 

 out to he that ozahc acid had been added to the samples (both sewage and 

 effluent water) of these months with the view of preyenting oxidation going 

 on in them during and after collection, and this prevented the estimation of 

 nitrogen in these forms by the process used. 



To test this some experiments were made as follows : — The October efflu- 

 ents, to which no oxalic acid had been added, gave 0*49 of nitrogen as nitrates 

 or nitrites per 100,000 parts ; to 500 cubic centimetres of this effluent 0-5 

 grain of oxalic acid was added, and the mixture allowed to stand for five 

 days ; no nitrites could then be discovered in it. Again, the effluent water col- 

 lected at Breton's during June 1876 was examined as follows : — " One portion 

 of it was analyzed, taking the sample from the full bottle ; at the same time 

 another portion was poured ofi' into a bottle, filling this bottle quite full, and 

 to this portion 18 grains of solid oxalic acid was added and this allowed to 

 stand for seven clear days, then analyzed. It was kept in a cool cellar. The 

 18 grains of oxalic acid to the quantity taken is in the proportion of 2 oz. to 

 the carboy of 12 gallons. 



(There is no doubt that the process of analysis accounts for the total disap- 

 pearance of the nitrates.) "■ — Dr. Ettssell. 



The " total nitrogen " in the effluent waters for those four months is 

 therefore represented in the Table as less than it should be. Leaving out 

 these four months, the " total nitrogen " in the effluent waters is, however, 

 higher than it was during the preceding year, this being chiefly due to an 

 increased amount of " nitrogen as niti-ates," the amount of nitrogen " not 

 nitrates " being very low throughout the year except in the month of June. 



Table III. is also given again in its original form, except that the effluent 

 water has only been gauged when it was mixed with the sewage, although in 

 collecting the samples for analyses portions were taken from all the effluent- 

 water drains ; and it is the results of the analyses of these mixed samples that 

 are used in calculating the amount of nitrogen in the effluent water returned 

 to the tanks. 



From this Table it appears that the true average amount of nitrogen in the 

 sewage was 5-53 parts per 100,000, and that the amount of nitrogen calcu- 

 lated to be applied to the farm in the sewage was 30-2525 tons; of this 

 quantity 0-1406 ton was collected in the effluent water repumped over the 

 farm. 



