Negative ionisable point

However we must thereby take into consideration that according to modern points of view an amphoteric protein is not really uncharged at the I. E. P., but contains an equal amount of positively and negatively ionised groups. 

At this point, it is necessary to stress that the brief introduction given above used positive ions as examples. However, it must be remembered that the same holds true for negative ions. Hence, an ionisation reaction such as that presented in equation (4) takes place simultaneously to that of equation (1) in an electron impact ion source. On a technical standpoint, negative ions can be observed as easily as positive ones a simple change in voltage potential within the source allows for directing these ions out of the source instead of their positive counterparts. 

The amphoteric colloids will at very low pH behave practically as " ionised colloids with basic character at high pH just as acid colloids , while in the intermediate region positive and negative charges occur together and just equilibrate one another at the isoelectric point (I. E. P.). 

If we consider for instance the monovalent ions Li, Na and K, then — exclusively from the point of view of field strength — on the surface of these ions the fixation on a given negatively charged ionised group will be easiest in the case of the smallest... 

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