SCIENCE. 



[N. S. Vol. XIX. No. 470. 



tigation of the processes involved in the 

 growth of plants is called for. Much has 

 been learned since Liebig founded the 

 science of agricultural chemistry. It was 

 he who pointed out some of the ways by 

 which it is possible to increase the fertility 

 of a soil. Since the results of his investi- 

 gations were given to the world the use of 

 artificial fertilizers has become more and 

 more general. 



But it is one thing to know that artificial 

 fertilizers are useful and it is quite another 

 thing to get them. At first bone dust and 

 guano were chiefly used. Then as these 

 became dearer, phosphates and potassium 

 salts from the mineral kingdom came into 

 use. 



At the Fifth International Congress for 

 Applied Chemistry, held at Berlin, Ger- 

 many, last June, Dr. Adolph Frank, of 

 Charlottenburg, gave an extremely inter- 

 esting address on the subject of the use 

 of the nitrogen of the atmosphere for agri- 

 culture and the industries, which bears 

 upon the problem that we are dealing with. 

 Plants must have nitrogen. At present 

 this is obtained from the great beds of salt- 

 peter found on the west coast of South 

 America — the so-called Chili saltpeter — 

 and also from the ammonia obtained as a 

 by-product in the distillation of coal, espe- 

 cially in the manufacture of coke. The 

 use of Chili saltpeter for agricultural pur- 

 poses began about 1860. In 1900 the quan- 

 tity exported was 1,453,000 tons, and its 

 value was about $60,000,000. In the same 

 year the world's production of ammonium 

 sulphate was about 500,000 tons, of a value 

 of somewhat more than $20,000,000. Of 

 these enormous quantities about three 

 quarters finds application in agriculture. 

 The use of these substances, especially of 

 saltpeter, is increasing rapidly. At pres- 

 ent it seems that the sticcessful cultivation 

 of the soil is dependent tipon the use of 

 nitrates, and the supply of nitrates is lim- 



ited. Unless something is done we may 

 look forward to the time when the earth, 

 for lack of proper fertilizers, will not be 

 able to produce as much as it now does, 

 and meanwhile the demand for food is in- 

 creasing. According to the most reliable 

 estimations indeed the saltpeter beds will 

 be exhausted in thirty or forty years. Is 

 there a way out? Dr. Frank shows that 

 there is. In the air there is nitrogen 

 enough for all. The plants can make only 

 a limited use of this directly. For the 

 most part it must be in some form of chem- 

 ical combination as, for example, a nitrate 

 or ammonia. The conversion of atmos- 

 pheric nitrogen into nitric acid would solve 

 the problem, and this is now carried out. 

 But Dr. Frank shows that there is another, 

 perhaps more economical, way of getting 

 the nitrogen into a form suitable for plant 

 food. Calcium carbide can now be made 

 without difficulty and is made in enormous 

 quantities by the action of a powerful elec- 

 tric current upon a mixture of coal and 

 lime. This substance has the power of 

 absorbing nitrogen from the air, and the 

 product thus formed appears to be capable 

 of giving up its nitrogen to plants, or, in 

 other words, to be a good fertilizer. It is 

 true that this subject requires further in- 

 vestigation, but the results thus far ob- 

 tained are full of promise. If the outcome 

 should be what we have reason to hope, we 

 may regard the approaching exhaustion of 

 the saltpeter beds with equanimity. But, 

 even without this to pin our faith to, we 

 have the preparation of nitric acid from 

 the nitrogen and oxygen of the air to fall 

 back upon. 



While speaking of the food problem, a 

 few words in regard to the artificial prep- 

 aration of foodstufi^s. I am sorry to say 

 that there is not much of promise to report 

 upon in this connection. In spite of the 

 brilliant achievements of chemists in the 

 field of synthesis it remains true that thus 



