Makch 11, 1921] 



SCIENCE 



239 



An Einstein four-dimensional manifold, de- 

 fining a permanent gravitational field, can 

 never he regarded as immersed in a flat space 

 of five dimensions. 



This applies in particular to the solar field 

 (defined say by the SchwaTzschild form), in 

 which the earth and the other planets are mov- 

 ing. The appropriate value of n must there- 

 fore be greater than 5 and less than 11. A 

 brief discussion shows that actually n ^ 6. 

 Therefore : 



TJie solar gravitational field can he repre- 

 sented hy a curved manifold of four dimen- 

 sions situated in a fiat space of six dimensions. 



This manifold can be written in finite form 

 and gives what may be called a geometric 

 model of the field in which we are living. 



The proofs of these theorems and the actual 

 equation of this model are appearing in cur- 

 rent numbers of the American Journal of 

 Mathematics, together with the full discussion 

 of the general results connecting light rays 

 and orbits in any field stated in Science, 

 October 29, 1920, pp. 413-414. 



Edward Kasner 



Columbia TjNrvEKSiTY 



THE AMERICAN CHEMICAL SOCIETY 



{Continued) 



FERTILIZER DIVISION 



F. B. Carpenter, chairman 

 H. C. Moore, secretary 



Kelp as a iasis of an American potash indus- 

 try: J. W. Tdreentine. 



Belationships of chemistry and the fertiliser in- 

 dustry: 0. H. MacDowell. 



A perfect fertilizer law: E. G. Peotilx. 



Boron in relation to the fertilizer industry: J. E. 

 Breckeneidge. 



The quantitative estimation of torax in mi-xed 

 fertilisers: J. M. Baetlett. 



Note on the determination of nitrogen in fer- 

 tilisers containing ioth organic and nitric nitrogen: 

 F. B. Caepentee. Notwithstanding the fact that 

 the modified Kjeldahl and Gunning methods have 

 been in nse for a number of years, the results ob- 

 tained by these methods in the hands of different 

 analysts on samples containing mixtures of organic 

 and nitric nitrogen are far from satisfactory. 



This is probably largely due to a wrong interpre- 

 tation of the official method. !Prom the standpoint 

 of the manufacturer this is quite a serious matter 

 and it se«ms desirable that the Association of Offi- 

 cial Agricultural Chemists should take such action 

 as is necessary to modify or at least change the 

 reading of the modified methods so that there may 

 be no misunderstanding of how they should be 

 carried out. 



Dicyanodiamide. A rapid, direct method for its 

 determination in cyanamid and mixed fertilisers: 

 EoLLA N. Hargee, presented by Oswald Schreiner. 

 The method depends upon the fact that when a so- 

 lution of silver piorate is added to a solution of 

 dicyanodiamide, the latter is quantitatively precipi- 

 tated as a double compound of silver picrate and 

 dicyanodiamide, CcH3(NO;)30AG, C^H.N,. This 

 new double compound we have named silver picrate- 

 mono-cyanoguanidine. It forms in small crystals 

 which quickly settle out of the solution and can be 

 separated upon a Gooch crucible very rapidly, so 

 that the analysis can be carried out in a very short 

 time. Neither cyanide nor urea give any precipitate 

 when their solutions are treated with silver picrate, 

 and determinations of dicyanodiamide carried out 

 in the presence of these compounds showed that 

 they have no effect upon the analysis. The molar 

 weight of the compound is 420.22, five (4.991) 

 times that of dicyanodiamide, a fact which greatly 

 enhances the accuracy of the method, since an error 

 of 1 mg. in the precipitate weighed will mean an 

 error of only 0.2 mg. of dicyanodiamide or 0.13 + 

 mg. of nitrogen. 



The changes taking place in cyanamid when used 

 in mixed fertilisers: Eolla N. Hargee, presented 

 by Oswald Schreiner. (1) When cyanamid is 

 placed in a mixed fertilizer containing acid phos- 

 phate and 5-10 per cent, of moisture, the eyana- 

 mide content decreases with great rapidity. (2) 

 This change is represented principally by, and in 

 many cases quantitatively by, the formation of 

 dicyanodiamide. (3) A given quantity of moist 

 acid phosphate is able to transform a limited 

 amount of calcium cyanamid. (4) Cyanamid is 

 not affected by dry acid phosphate. (5) Moisture 

 alone is able to cause the conversion of cyanamid 

 to dicyanodiamid, but the change is much slower 

 than when acid phosphate is present. Since it 

 has been repeatedly shown that dicyanodiamid is 

 valueless as a fertilizer material and, moreover, is 

 toxic to many plants, the formation of this com- 

 pound in fertilizer materials seems undesirable. 

 Prom the results of this study it would seem that 



