PRESIDENTS ADDRESS. \J 



but containing them in a state as readily available as possible 

 for the cereals to absorb. How to get our raw materials into 

 this readily available state is precisely the problem on which 

 all our chemical energies should have been concentrated for some 

 time past. 



Regarding the utilisation of our phosphate deposits there 

 is much work to be done, both on the field and in the laboratory. 

 The Saldanha Bay deposits were first investigated in the Cape 

 laboratories about nine years ago,* but until the war quickened 

 the pulse, very little was done in the direction of ascertaining the 

 best way of converting these aluminium-iron phosphates into a 

 form available to plants, and of their value in the unconverted 

 form we know scarcely anything more from field experiments 

 than we knew nine years ago. With regard to nitrogen, we 

 scarcely realise that we live at the bottom of an atmospheric 

 ocean of which the bulk consists of free nitrogen — free, not only 

 in the chemical sense, but likewise so free that no war can cut 

 us off from it as the present war has cut us off from the essen- 

 tially German potash ; and not alone free, but abundant, for 

 there is a weight of seven tons of this nitrogen above every 

 square yard of the earth's surface. 



Now there are two nitrogen cycles in constant operation, and 

 in each cycle the animal kingdom has a definite part to perform. 

 There is a cycle of free nitrogen, and there is a cycle of com- 

 bined nitrogen. The former is relatively simple, the latter more 

 complex. We breathe in the free nitrogen of the atmosphere' and 

 exhale it again, thus restoring it to the air unchanged, and as 

 free as it was before. The. combined nitrogen taken by animals 

 as a constituent of their food undergoes a change within the 

 animal body, is returned to the soil as new nitrogenous com- 

 pounds in the form of manure, and becomes converted by the 

 soil bacteria into nitrates, which are capable of being absorbed 

 by the vegetation. Animals feed on and assimilate this vegetable 

 ifoodstufif. and so the cycle begins anew. The two nitrogen 

 cycles — ^^the.breathinw cycle and the feeding cycle — move in per- 

 fect independence of each other, and the problem of the chemist 

 — a problem that has been largely solved within little more than 

 the last dozen years — has been to bring free nitrogen within 

 the sphere of operation of the cycle of combined nitrogen. I 

 say this problem has been to a great extent solved. Chemistry 

 has discovered two methods which are commercially practicable 

 whereby the nitrogen of the air can be "' fixed," as it is called. 

 One is the manufacture of cyanamide, which can then be used 

 directlv as a fertiliser. For this manufacture two things are 

 essential — almost pure nitrogen and electrical energy as a source 

 of heat. The nitrogen is obtained by liquefying air. and allow- 

 ing the liquid air to evaporate, when the nitrogen boils away 

 first and is collected. This " fractional distillation " of the 

 liquid air is generally carried out in a Linde or Claude apparatus. 



* C. F. Juritz : Report of Senior Anal.vst, Cape of Good Hope (1909), 

 159. 



