378 SCIENCE PROGRESS 



process will not proceed with measurable speed at ordinary 

 temperatures, because there is almost none of this type of 

 radiation present in a material system at ordinary temperature. 

 To render the process observable it is necessary to expose the 

 material to an external source emitting this high-frequency 

 radiation in sufficient quantity. The conditions are in fact 

 those met with in photo-chemical reactions, so-called. On 

 raising the temperature of the material by ten degrees under 

 these conditions there is still no sensible increase in the density 

 of the radiation of the effective type, and the process is, in 

 fact, independent of temperature. This is already known to 

 be approximately the case with photo-chemical changes. What 

 is practically true of processes requiring radiation of the fre- 

 quency io 15 is even more rigidly true of processes which require 

 a frequency of the order io 21 . Perrin's calculation that 

 the frequency of the external radiation causing radio-active 

 change is of this order is therefore in agreement with the fact 

 that the temperature alterations which can be brought about 

 under ordinary experimental conditions are absolutely without 

 influence upon the rate of radio-active transformations. 



At the present time the hypothesis lacks a direct 

 experimental basis. If its originator is able to make progress 

 in this direction it will constitute one of the most striking 

 advances of physical chemistry. 



ORGANIC CHEMISTRY. By P. Haas, D.Sc, Ph.D., University 

 College, London. 



During the last quarter a number of communications dealing 

 with vitamines have been published, showing the ever-increas- 

 ing attention which is being paid to this interesting class of 

 compounds. The report of the Lister Institute for Preventive 

 Medicine for 1919 contains an account of the work done in 

 connection with the anti-scorbutic accessory factor in common 

 food-stuffs. From this it would appear that the juice of the 

 lemon is far superior in antiscorbutic activity to that of the 

 lime either fresh or preserved ; it has, moreover, been found 

 that the " lime juice " originally employed in combating 

 scurvy in the British Navy was in those days actually prepared 

 from lemons. Swede juice is found to be the most efficient 

 substitute for the juice of the lemon or the orange. Vegetables 

 lose practically all their antiscorbutic properties in tinning, 

 and, as their food value is not high, they are not economical. 

 Dried vegetables likewise are deficient in antiscorbutic pro- 

 perties. Dried milk has considerably less antiscorbutic action 

 than fresh or scalded milk, but there is not much difference 

 in the growth-promoting properties of the two. By making 



