34 THE ROYAL SOCIETY OF CANADA 



Thus the sugars gave a strong positive reaction and the blue color 

 in all cases was intensified by the addition of alkali. 



The second by Neuberg (4) showed that ammonium salts and many 

 organic bases gave a strong positive reaction when the "ninhydrin" 

 test was applied to them. Some of these results were in direct con- 

 tradiction to the earlier results of Abderhalden and Schmidt (loc. cit.) 

 as is shown in the following table: 



Abderhalden & Schmidt. Neuberg.. 



Suprarenin — + 



Glucosamine — + 



Ammonium Bicarbonate — . + 



Ammonium Oxalate — + 



In view of the results it will be seen that a complete critical inves- 

 tigation into the reaction is of prime importance both from a chemical 

 and a physiological point of view, for it is not very easy to discern 

 how such a series of compounds as glycerol, lévulose, alanine, ammon- 

 ium acetate, and ethylamine can give one and the same reaction 

 with triketohydrindene hydrate. Halle, Loewenstein, and Pribram, 

 indeed, recognized two blue colorations, one produced by amino 

 acids, and a second produced by alcohols, ketones, and aldehydes. 

 They distinguished them by several characteristics. Thus the colora- 

 tion produced by amino acids could be obtained in a vacuum in absence 

 of oxygen and was not intensified by the addition of alkali ; whereas the 

 coloration given by glycerol required the presence of oxygen and be- 

 came much more intense on the addition of alkali. They do not 

 agree with Ruhemann's view on the constitution of the blue color 

 produced with amino acids, but do not themselves put forward any 

 definite statement as to the constitution of either of their own two 

 colorations. 



Ruhemann, however, had previously noticed that a blue coloration 

 was given by the action of the hydrates of the alkali metals upon 

 hydrindantin, and that the latter compound could not be reprecipi- 

 tated from the blue solution by the action of acids. He noticed how- 

 ever that the blue solution was rapidly decolorised by shaking with 

 air. 



The delicacy of the "ninhydrin" reaction with amino acids is 

 undoubted. Abderhalden and Schmidt found that glycine gave a 

 blue coloration when 1 part in 65,000 parts of water and histidine 

 when only 1 : 74,000. Utilising the delicacy of the reaction Harding 

 and MacLean (5) have devised a method for the colorimetric estimation 



