698 

 TABLE 4. 



The limit, al wliicli irregular series do not appear any more — 

 the top of the pappy range — is found for nitric acid, sulphuric 

 acid and acetic acid at almost the same percentage of latex, but for 

 iij'drochloric acid it is somewhat higher. With all tlii.s we have to 

 bear in mind that with nitric acid in a mixture with 60°/,,, with 

 sulphuric acid in one with 70 V». «■ distinct interruption in the series 

 can still be observed, owing to the coagnlum, at a level of the 

 above-mentioned top, being softer than at higher or lower concen- 

 trations of acid. A striking difference in the position of this top 

 cannot therefore be stated with the four acids. 



On the other hand there is an undeniai)le difference with regard 

 to the top of the really liquid range, which, with iiydiochloric acid 

 extends to much higher latex-concentrations, than with the three 

 remaining acids. 



In the upper limit of tiie liquid range, i.e. the beginning of the 

 upper curdling range, and likewise in the upper limit of tiiis range, 

 i.e. ilie lower limit of the second range of coagulation, the difference 

 is very sinking loo. With acetic acid these limits are by far the 

 highest; then follows hydrochloric acid, about halfway lower nitric 

 acid, and half way lower again sulphuric acid. If we assume, that 

 in the second liquid range the colloid rubber particles have changed 

 their charge from negative into positive, the stronger coagulating 

 action of the bivalent sulphate-ion would be fully explained; mono- 

 valent ions then would show a decided difference in the series 

 nitrate-, chlorine-, acetate-ion. 



A comparison of the action of the tour acids in the first range 

 of coagulation seemed of particular interest to us, viz. with small 

 latex-concentrations, where, with a small increase of the acid- 



