498 M. It. MEACHAM, J. H. HOPFIELD AND S. F. ACREE 



the same concentration employed in the first solution) and con- 

 taining also any desired amount of hydrochloric or other strong- 

 acid necessary to liberate any part or all of the asparaginic and 

 phosphoric acids. It is clear that in this way we can keep the 

 concentration of the asparaginic and phosphoric acid (or the 

 salts of these) constant at any desired concentration, say M/10, 

 and at the same time change the hydrogen ion concentration from 

 that of the very alkaline solution up to that of the very acid so- 

 lution obtained when a sufficient volume of the solution of hy- 

 drochloric, asparaginic and phosphoric acid is added to the alka- 

 line solution. It is furthermore clear that a similar procedure 

 would enable the operator to make a choice of the constant con- 

 centration at which he could keep the cations and anions in mak- 

 ing such a titration curve. Without further discussion, it is 

 clear that the one solution of the mixture of phosphoric and 

 asparaginic acids could be made to give any desired hydrogen 

 ion concentration by simply adding varying known quantities of 

 alkali and water to keep the solutions standard. Likewise, the 

 one solution of disodium (or potassium) asparaginate and tri- 

 potassium (or sodium) orthophosphate could be made to give 

 any desired hydrogen ion concentration by simply adding cal- 

 culated quantities of hydrochloric acid. The above described 

 method of mixing a very alkaline and a very acid solution of 

 equimolecular parts of asparaginic and phosphoric acid (in say 

 M/10 concentrations of each acid in both solutions) will perhaps 

 be a more convenient way of making a titration curve and of 

 getting any desired hydrogen ion concentration by mixing the 

 proper volumes of the two solutions. The hydrogen ion concen- 

 tration is measured easily by means of the hydrogen electrode, a 

 standard calomel or hydrogen comparison electrode and the 

 Loomis-Acree (1911) method of eliminating contact potentials by 

 the use of 4. In potassium chloride. The errors of the Bjerrum 

 extrapolation method are discussed in another article. 



Mr. J. H. Hopfield has completed a titration curve on aspara- 

 ginic acid from the very acid to the very alkaline regions. The 

 ionization constants of the two acid groups and the basic group 

 have been calculated from his data and will be reported in a 



