37^ TRANS. ST. LOUIS ACAD. SCIENCE. 



Where there is evolution of heat in chemical reac'ions thtre 

 is necessarily condensation. Our experiments proved this actu- 

 ally to be the case. Again, where there is contlensation the 

 substances reacting upon one another must be united more 

 firmly than when each is in the free state. In other words, 

 the vapor tension must be less. This we actually found to be 

 the case also. The phenomena of hydration of colloids are by 

 no means unimportant. A proper understanding of their values 

 is absolutely necessary for a true understanding of the economy 

 of the animal body. As yet there have never been drawn into 

 consideration these factors. Nor can we draw them into cal- 

 culation until many more investigations of all the colloid hy- 

 drations in the animal frame will have been made. 



ELiEfTRICAL, CONDUCTIVITY. 



In 1SS3 Prof. E. Wiedemann demonstrated in his experiments 

 on solutions of zinc sulphate in water and glycerine, that the reis 

 no relationship between coefficients of friction and galvanic con- 

 duction. For a solution of zinc vitriol in water and glycerin the 

 coefficients of friction were to one another as i : 68.7, the resist- 

 ances of galvanic conduction as i : 12.1. In continuation of these 

 experiments I have made, at the ins^tigation of Prof. Wiedmann, 

 an examination of the behavior of zinc vitriol dissolved in gela- 

 tine solutions of different strengths at different temperatures. 

 Experiments on the same subject have been published since the 

 time of completion of my work by Arrhenius and B. v. Tietzen- 

 Hennig. However a communication of my resultswill not be 

 superfluous as my experiments were made on much more con- 

 centrated solutions of gelatine. 



The solutions employed by me contained 25 p. ct. and 50 p. ct. 

 of gelatine, and 2 p. ct., 54 p.ct. and 10 p. ct. of zinc vitriol. The 

 mixtures of definite concentrations of zinc vitriol, water and gela- 

 tine were made in the following manner : 



The gelatine was first weighed out in a beaker glass, and the 

 quantity of water necessary for a certain concentration then added. 

 The solution was boiled in a brine-bath and the necessary amount 

 of salt added, i'he water lost by evaporation was replaced when 

 the solution was complete. To obtain a 50 p. ct. gelatine solution 



