GSi 



REPORT — 1884. 



which amides or albuminoids were employed, the formation of ammonia preceded 

 the production of nitric acid. 



As ammonia i.s so readily nitrifiable, we may safely assert that every nitroj^en- 

 ous substance which yields ammonia wlion acted on by the org-anisms present in soil 

 is also nitritiable. 



Certain Conditions havitiff Great Influence on the Process of Nitrijicatiun . — If we 

 .suppose tinit a eolutiou containinjr a nitritiable substance is supplied witli the 

 nicrifyiufi; orjranism, and with the various food-constituents necessary for its growth 

 und activity, the rapidity of nitrilication will depend on a variety of circumstauct's:— 

 i(l) The degree of cmiceutratiou of the solution is important. Nitriti ation always 

 couiuiences first in the wealiest solution, and there is probal)ly in the case of every 

 -solution a limit (d" concentration beyond winch intritication is impossible. (2) The 

 temperature lias great influence. Nitriticatiou proceeds far icoro rapidly in summer 

 tthan in winter. (■\) Tlie presence or absence of light is important. Nitrification 

 li most rapid in darkness; and in tiie case of solutions, exposure to strong light 

 may cause nitrilication to cease altogetlier. (4) The presence of oxygen is of course 

 -essential. A thin layer of solution will nitrify sooner than a deep layer, owing to 

 the larger proportion of oxygen available. Tiie inlliieuce of depth of fluid is most 

 conspicuous in tlie case of strong solutions, (o) The quantity of nitrifying organism 

 present has also a nnirkeil ell'ecl. A solution seeded with a very small amount of 

 organism will for a long time exhibit no nitrification, the organism being (uidike 

 s^une otiier bacteria) of veiy .slow growtii. A solution receiving an abundant supply 

 of the ferment will exhibit spi-edy nitrification, and strong .solutions may by this 

 means be successfully nitrified, which with small sceding-s would prove very refrac- 

 ty.iry. The speedy nitrification which occurs in soil (far more speedy than in experi- 

 ments in solutions under any conditions yet tried) is jiroljably owing to the great 

 mass of nitrifying organism wliich soil contains, and to the thinness of the liquid 

 layer '.v'hich covers tiie soil particles. (G) The rapidity of nitrilication also depends 

 <ni the degree of alkalinity of the solution. Xitritication will not take place in an 

 acid solution, it is essential that some base sliould be prese!it with which the nitric 

 acid may combine ; when all available base is used up nitrification ceases. It aj)- 

 peared of interest to ascertain to what extent nitrilication would proceed in a diliiti! 

 .s)lutiou of urine witliout the addition of any substance save the nitrifying ferment. 

 As urea ia converted into ammonium carbonate in the lirst stage of the action oftlui 

 fn-ment, a supply of salifiable base woidd at first be ])resent, but woidd gradually 

 to consumed. The result of the experiment showed tliat only one-half the quantity 

 of nitric acid was fcjrmed in the simple urine solution, as in similar solutions cnii- 

 taining calcium and sodium carbotiate. The nitrilication of the urine had evidently 

 proceeded till the whole of the ammonium iiad been changed into ammoniuiu 

 citrate, and the action had then ceased. This fact is of practical importance. 

 tSewage will Ite tiioroughly nitrititnl oidy wiien a sullicient sujjply of calcium car- 

 bonate, or .some otiier ba.se, is available. If instead of calciimi carbonate a .sol- 

 uble alkaline salt is present, the quantity must be small, or nitrification will Iw 

 seriously hindered, yodinm carbonate begins to have a retarding influence on the 

 commencement of nitrification when its amount exceeds oOO milligrammes ])er litre, 

 and up to the present time I have been unable to produce an effective nitrilication 

 in solutions containing I'OOO gramme ])er litre. Sodium hydrogen carbonate hin- 

 ders far less the commencement of nitrification. Ammonium carbonate, when above 

 fc certain amomit, also prevents the commencement of nitrification. The strongest 

 solution in wiucli nitrilication has at present commenced contained ammoniuiu 

 carbonate equivalent to oGS milligrammes of nitrogen per litre. This hindrance of 

 nitrification by thfi presence of an excess "•' ammonium oarbomite effectually pve- 

 vents the nitrification of strong solutions of urine, in which, as already mentioned, 

 emmonium carbonate is the first i)roduct of fermentation. Far stronger solutions 

 of aniiaonium chloride can be nitrified than of ammonium carbonate, if the solution 

 of the former .salt is supplied with calcium carbonate. Nitrification has in fact 

 i;omm -need in chloride of ammonium solutions containing more than two grammes 

 ©f nitrogen per litre. 



The details of the recent experiments, some of the results of which we have 



