462 Dr. T. Oarnelley on the 



portional to the equivalent of the body dissolved. Graham 

 (Phil. Trans. 1861, p. 373; Chem. Soc. Journ. xv. p. 427) 

 afterwards found, as regards alcohols, ethers, and organic 

 acids belonging to the same homologous series, that the rate 

 of flow was the greater the lower the body was in the series. 

 He also found that the rate of an acid is slower than that of 

 an ether with which it is metameric. More recently still, 

 Schultze (Chem. Centr. 1872, p. 705) found, as the result, of 

 his experiments, that in respect to solutions of salts of K, Na, 

 and Li, as also to solutions of salts of Ba, Sr, Ca, and Mg, the 

 velocity of flow is the greater the greater the atomic weight of 

 the metal, and that there is but little difference between the 

 rate of flow of the chloride, bromide, and iodide of one and the 

 same metal. But it was reserved for Hannay (Nature, 1879, 

 xix. p. 378) to show that solutions containing equivalent 

 quantities of the respective salts must be used if the influence 

 of the chemical composition on the rate of flow is to be fully 

 made out. " By the use of such normal solutions, he found 

 that the rate of flow does not depend on any of the mechanical 

 properties of the salts, such as crystalline form, molecular 

 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 K and 

 Na formed by the same acids have a constant difference. In 

 like manner, each metalloid and acid radical has a value which 

 is continued in all its combinations. The greater the combi- 

 ning value of the element, the quicker its rate of flow. Thus 

 K has a higher rate than Na, Ba than Sr, and so on. The 

 rate of flow also varies with the amount of energy in the com- 

 pound : thus nitrates stand highest, as they contain most 

 energy, then chlorides, and lastly sulphates, which are ex- 

 hausted compounds." It is therefore evident from these facts 

 that the chemical equivalents may be found by determining 

 the rate of flow of their compounds. 



In a paper read before the Vienna Academy (Nature, 1879, 

 xx. p. 277) on the specific viscosity of liquids and its relations 

 to chemical composition, Pribram and Handl have shown : — 

 (1) That the substitution of CI, Br, I, or N0 2 for H in a mo- 

 lecule causes, in all cases, an increase in the time of flow 

 through a capillary tube. (2) That this increase is least on 

 the substitution of CI, and more successively in those of Br, 

 I, and N0 2 . (3) That the increase in the rate of flow depends 

 not only on the nature of the element, but also on its position 

 in the molecule. 



Capillarity. — I have already referred to the fact (ride supra. 



