19-21.] 



Synthetic Nitrogenous Fertilisers. 



1043 



about ±.'37 5s. ; and unless it can be produced at this figure it is 

 not likely to command an extensive sale. 



Ammonium Carbonate. — It would not be a cLimcult matter 

 to prepare ammonium carbonate synthetically, and as a 

 fertiliser it would have the advantage that it could not cause 

 soil acidity, while it would be at least as effective as sulphate 

 of ammonia. Samples have already been prepared: one sent 

 to the Eothamsted laboratories contained 25.5 per cent, of 

 nitrogen and another contained 18.4 per cent. Ordinary sul- 

 phate of ammonia contains about 20 per cent. Unfortunately, 

 however, the material is very volatile and rapidly loses 

 ammonia, and until this difficulty can be overcome it offers 

 little prospect to the farmer. 



Ammonium Chloride. — From the financial point of view the 

 most promising synthetic ammonium salt is the chloride, which 

 is likely to be turned out in great quantity in this country in 

 the near future. In the past it has been practically untested 

 by British investigators; the large production of sulphate of 

 ammonia appeared to rule out any possibility of the manufac- 

 ture of the chloride. For many years it was used at 

 Eothamsted in conjunction with sulphate of ammonia, but no 

 careful comparison between the two salts was made. 



On general grounds it might be supposed that the chloride 

 and sulphate of ammonia must be of equal fertiliser value. 

 There is, however, much physiological evidence to the effect 

 that chloride under certain conditions may be harmful to plant 

 growth. It by no means follows that this would happen in 

 practice; whether it would or not can only be ascertained by 

 trial. In view of the technical importance of the salt, an 

 extended investigation is to be made. 



Urea. — During the War several patents were taken out in 

 Germany for the manufacture of urea as a fertiliser. Urea has 

 the advantage of being highly concentrated, containing no less 

 rhan 47 per cent, of nitrogen, an enormous advantage for the 

 export trade. Whether it would have equal advantages for the 

 home trade is not so clear. A field experiment is being carried 

 out this year at Eothamsted. 



Cyanamide or Nitrolim. — This substance is already well 

 known as a fertiliser, although during the War it was not 

 readily obtainable by farmers. The growth of its manufacture 



