280 Mr. J. B. Hannay. On the Microrheometer. [Jan. 23, 



been called in this country transpiration, -while in other countries no 

 distinct name has been adopted ; and as the English word is already 

 in use in French for another purpose, and properly applies to gases 

 (the laws relating to which are quite different), the author proposes 

 to use for liquids the term " Microrheosis," from jLiacp6s and pew, the 

 instrument being called the microrheometer. The form of apparatus 

 which the author finally adopted is figured in the paper, and is so 

 arranged that when the liquid is introduced, as many experiments as 

 may be desired may be tried, and the pressure and temperature, as 

 well as the atmosphere in which the experiment is conducted, may be 

 varied, while the thermometer indicating the temperature is at the 

 mean point of the system. The author gives a curve for water from 

 0° to 100°, the differences of rate being smaller as the temperature 

 rises. 



Various salts are then examined, being dissolved to form "normal" 

 solutions ; but as the solubility of some salts is too low for such solu- 

 tions, the effect of the amount of salts dissolved is determined. This 

 is found to be directly proportional to the amount of salt in solution. 

 Values for many salts in solution are then given, each number being 

 the mean of ten experiments, and the probable error of the mean is 

 calculated in each case. The conclusions arrived at are these. The 

 rate of flow does not depend on any of the " mechanical " features of 

 the salt, such as crystalline form, specific volume, solubility, &c. ; but 

 upon the mass of the elements forming the substance and the amount 

 of energy expended in its formation. Each element has a value of its 

 own, which is continued in all its compounds. Thus all the salts of 

 potassium and sodium formed by the same acids have a constant diffe- 

 rence. In like manner each metalloid and acid radicle has a value 

 which is continued in all its combinations. Then the greater the com- 

 bining value of an element the quicker is its microrheosis ; thus 

 potassium has a higher rate than sodium, barium than strontium, 

 strontium than calcium, and so on. The microrheosis also varies with 

 the amount of energy in the compound ; thus nitrates stand highest, 

 as they contain most energy ; then chlorides ; and, lastly, sulphates, 

 which are exhausted compounds. 



The instrument, bringing to light as it does the fundamental rela- 

 tions of combining weight and energy in chemical action, will be 

 of the utmost importance in chemical physics, as by its use, not 

 only will the amount of energy evolved in reactions be determined, but 

 the mass combined ; or, in other words, the chemical equivalent of the 

 elements involved will be found. 



