36 CHEMICAL CONSTITUENTS OF BODY AND FOOD. 



Accordingly, amido-compounds, leucines (C m H 2m+1 NO.,), and leuceines 

 (C n H 2n _iNOo), were mixed with about 10 per cent, of urea, and finely 

 powdered. The mixture was dried at 110 C., intimately mixed with 1/5 

 times its weight of phosphoric anhydride, and heated in an oil bath. At 

 120 C. there is no change; at 125 dehydration takes place rapidly, and 

 the mixture becomes pasty, but solidifies to a compact solid mass without any 

 darkening. This is dissolved in water, the solution mixed with excess of 

 alcohol, and the pasty precipitate so produced washed with alcohol and 

 re-dissolved in water. Phosphoric acid is removed by baryta, and the filtered 

 liquid when concentrated yields an amorphous product soluble in water, but 

 precipitated in a curdy form on the addition of alcohol. 



Aqueous solutions of this product are precipitable by most of the other preci- 

 pitants of proteids ; it gives the biuret and the xanthoproteic reactions. When 

 burnt it gives the characteristic odour oi burning nitrogenous animal matter. 



The product he obtained does not give all the proteid reactions ; 

 it is, for instance, not precipitable by acetic acid and ferrocyanide of 

 potassium ; and the evidence as to its proteid nature is otherwise hardly 

 conclusive, because the colour tests for proteids are given by many of 

 the decomposition products of albuminous matter. The partial success 

 obtained will, however, point the way for future attempts, and so far 

 as it goes, is in favour of Schiitzenberger's ureide theory of proteid 

 constitution. Complete success could hardly have been anticipated 

 from such an experiment, because no means were taken to ensure the 

 presence of sulphur, an element present in all proteids. Moreover, 

 in the synthesis, no aromatic substance was introduced; this, how- 

 ever, is not absolutely necessary, as the formation of aromatic from 

 fatty compounds by heat is a familiar chemical change (see p. 34). 



Grrimaux's experiments. Some years previous to Schiitzenberger's 

 work, Grimaux l had obtained, by somewhat simpler processes, substances 

 which even more resembled proteids in their reactions than Schiitzen- 

 berger's. He was engaged in studying the properties of certain sub- 

 stances, inorganic and organic, which he termed " colloides" and of those 

 which he prepared the three which especially bear on the present 

 question are the following : 



(a) Colloide amidobenzoique. This is made by heating, to 125 C., 

 meta-arnidobenzoic acid in a sealed tube, with one and a half times its 

 weight of phosphorus pentachloricle, for ninety minutes. The product is 

 a white friable powder ; this is washed repeatedly with boiling water to 

 remove all phosphoric acid. The remaining substance Grimaux supposes 

 to be an intramolecular anhydride, formed by the union of several mole- 

 cules of meta-amidobenzoic acid, with the elimination of water. When 

 ammonia is added, it dissolves slowly in the cold, but rapidly on heating. 

 The solution obtained is evaporated in vacuo, at a low temperature, and 

 the resulting solid is a transparent jelly which dries into translucent, 

 yellowish plates, which in their physical properties resemble dried 

 serum albumin. 



(&) A colloid which is similarly prepared, except that the temperature 

 in the sealed tube is allowed to rise to 135 C 0. 



(c) Colloide aspartique. This is made by the action of a current of 

 gaseous ammonia on solid aspartic anhydride, heated to 170 C. The 



1 Compt. rend. Acad. d. sc., Paris, tome xciii. p. 771 ; xcvii. pp. 231, 1336, 1434, 1485, 

 1540, 1578 ; Rev. sclent., Paris, April 18, 1886 ; this article gives a summary of the other 

 papers. 



