vi ACIDITY : BASICITY OF AMINO-ACIDS 213 



or splitting of esters, Winkelblech combined Walker's 1 principle of 

 estimating the strength of feeble bases by studying the hydrolysis of 

 their chlorides, with the analogous method of Shields, 2 who studied 

 the hydrolysis of the sodium salts of feeble acids. In this way it was 

 possible to determine for each amino-acid the relative strengths of its 

 acid and basic radicals. 



Winkelblech gives the following ratios of the acidity to the basicity 

 of certain amino-acids : 



Acidity to basicity. I Acidity to basicity. 



Aspartic acid . ^. . 5 3 millions:! Asparagin 3000:1 



0-amino-benzoic acid . /. 4 millions : 1 Alanin . 240 : 1 



p- 2-6 millions : 1 Glycocoll . 120 : 1 



0'5 millions : 1 



Leucin . 115:1 

 Sarcosin 72 : 1 



Further information on these complicated relationships, and particularly 

 on the points in which amphoteric electrolytes differ from ordinary 

 electrolytes, will be found in Walker's recent paper. 3 



The most remarkable property of amino-acids is their strong hydro- 

 lysis, which means that the salts which amino-acids form with other 

 acids or bases are very readily broken up by the ions of water. If a 

 strong base is linked to a strong acid, if, for example, equivalent 

 amounts of hydrochloric acid and of caustic soda are dissolved in 

 water, then the acid hydrogen-ion of the HC1 unites with the alkaline 

 hydroxyl-ion of the NaOH to form neutral water, while the sodium- and 

 the chlorine-ions form a neutral salt. In this case the negative chlorine- 

 ions and the positive sodium-ions possess a great electro-affinity for one 

 another, and therefore they do not unite with either the feeble, 

 acid hydrogen-ions or the feeble, alkaline hydroxyl-ions of the water. 

 But if, instead of two such strong radicals as sodium and chlorine, there 

 be present one feeble radical, e.g. an amino-acid, in combination with a 

 strong acid or a strong base, then the strong radical will not join up 

 with the amino-acid, which is a more feeble radical than are the ions 

 of water, but will combine with one of the ions of the water. 



Generally speaking, any amphoteric electrolyte H'R'OH will 

 form, according to Walker, the ions H, OH', HR, and ROH', while 

 the non-ionised portion must be either in the state of a hydrate H R OH 

 or that of an anhydride R. Therefore an equilibrium in the solution 

 depends on the factors 



+ - + 



H OH ROH RH HROH R. 



1 James Walker, Zeitschr. f. physik. Chem. 4. 319 (1889). 

 2 Shields, ibid. 12. 167 (1893). 3 James Walker, ibid. 49. 82 (1904). 



