WALL-SALTPETRE AND PLANTATION-SALTL'KTRK 293 



changes occurring in the reaction, but these can merely be alluded to here. 

 Godlewski ascertained that by no means the whole of the ammoniacal nitrogen 

 eliminated during the nitrification is recovered as nitrous or nitric acid, but that 

 a portion is liberated in its elementary condition, and escapes from the solution 

 undergoing nitrification. It may be opined that this loss is not immediately 

 connected with the action of the nitrifying bacteria, but is only an associated 

 phenomenon produced by the reaction of the N 3 O 3 on the still undecomposed 

 NH 3 , in accordance with the equation 



N 2 3 + 2NH 3 = 3 H 2 + 2N 2 . 



The reason for this is that the nitrous acid liberated does not in every part of the 

 liquid come into immediate contact with the carbonate which would protect it 

 from the action of the ammonia. 



208. Wall-Saltpetre and Plantation-Saltpetre. 



The particulars already given of the life-conditions of the nitrifying bacteria 

 will explain the origin of wall-saltpetre, i.e. the corroding efflorescence of salt- 

 petre on masonry. This substance is a white snow-like mass, consisting princi- 

 pally of crystals of calcium nitrate, and occurring with particular frequency on 

 the walls of stables and closets. It is precisely in such places that the fission 

 fungi under discussion find an abundance of the food-stuffs they require : the 

 ammonia salt is supplied by the urea absorbed by and hydrated in the walls ; 

 calcium carbonate and a little alkali are present in the brickwork, and there is 

 no lack of the necessary oxygen. Consequently all the preliminary conditions 

 favouring the activity of the nitrifying bacteria introduced in dust, &c., are 

 fulfilled. However welcome this activity may be when restricted to the soil, it 

 is entirely undesirable in brickwork, the latter being gradually corroded and 

 rendered brittle by the calcium nitrate produced. Sprinkling the walls with 

 powerful antiseptics, such as antinonnin, may, however, afford a remedy. That 

 the phenomenon is really due to the nitrifying bacteria has been proved by the 

 researches of 0. HELM (II.) and G. TOLOMEI (II.). 



A few words must also be devoted to the saltpetre plantations. Since the 

 discovery of the South American deposits of nitrate of soda, which substance 

 can be converted into saltpetre by treatment with potassium salts, the production 

 of plantation-saltpetre has decreased. It will, however, come to the front again 

 whenever the Chilian beds are exhausted. In fact, the production of saltpetre 

 for agricultural purposes by this method is even now worthy of consideration. 

 The quantity of Chili saltpetre imported by European countries is very con- 

 siderable, arid large sums of money are annually disbursed to South America 

 which might be retained by producing the saltpetre at home. The accomplish- 

 ment of this project necessitates a searching investigation of all the conditions of 

 nitrification, in order to ascertain how the reaction may be suitably controlled. 

 The result would be that, instead of using expensive foreign nitrate, the ground 

 would be manured with cheap sulphate of ammonia, now formed as a waste 

 product in home gas-works and coke-factories, and put upon the market in con- 

 stantly increasing quantities. The consequent freedom from the hands of 

 Chilian speculators would be a great gain from the point of view of national 

 economy. Moreover, this method of manuring presents another advantage from 

 the standpoint of the agricultural economist. As is well known, the soil has no 

 power of fixing nitrates, a certain portion of the added saltpetre invariably as 

 P. DEHERAIN (III. and IV.) and others have shown escaping in the drainage- 

 water, so that more has to be added to the soil than is recovered in the crop. 

 This disadvantage does not attach to manuring with salts of ammonia, since they 



