562 



These curves indeed do not, like the others, descend regularly 

 but show first, to about \/^^ grammolecule, a considerable descent, 

 and afterwards suddenly descend much less, so that they cut a 

 number of the other curves. 



I constantly found this sudden modification of direction at \/',„ 

 grammctlecule in repeated experiments. 



With regard to the other salts, they appear to retard the urease 

 stronger in the following order -. 



NH/ <K- <Na <Sr <Ba" 



Up to 7»o grammolecule per Liter the curve for Ca " corresponds 

 about with that of Sr "' , and that of Mg ' with that ofBa' . With 

 the experiments with colloids we do not find as a rule the whole 

 series mentioned, the series is most complete in the experiments of 

 Pauli about the increase of the temperatnre of congealment of 

 solutions of albumen viz. : 



NH, • < K • < Na • < Ba • < Mg " 



With the exception that here Mg " comes after Ba ", whilst these 

 two melals on urease to Vso g'"^'T^'ïï''ol. per Liter show an equal action, 

 there is perfect agi'eement between the two series. 



The order of succession NH/ , K ' , Na ' , Mg' occurs a.o. in 

 experiments about the coagulation of albumen by an earthalkali salt. 



The coagulation is namely favoured by salts of these four metals 

 in the indicated order. 



The series K " <^ Na ' <^ Sr " <^ Ba ' <^ Mg " is found at lowering 

 the melting-point of a gelatine-gel by neutral salts. 



One might di-aw the following normal series, from the different 

 series that occur in literature for colloid-phenomena: 



NH/ <C K <^ Na ■ <^ Sr '■ <^ Ba "' <^ Mg "' , which corresponds 

 consequently with that which is found for the influence of the 

 action of urease. Occasionally Ca " occurs in another place in one 

 series than in the other, now between K ' and Na ' , now after Ba " . 



This depends presumably on the concentration that has been used; 

 it occurs likewise with urease, as the calciumcurve cuts a number 

 of other curves above the concentration 7»o "lo^- P©'" Liter. 



IL Anions. 



When we studied the influence of anions on the action of urease 

 we used potassium salts. Only those acids were used the potassium 

 salts of which are neutral, the action of urease, like other ferment- 

 processes being very sensitive to modification of the hydrion- 



