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XII. Intelligence and Miscellaneous Articles* 



ON THE FLOW OF SALINE SOLUTIONS THROUGH CAPILLARY TUBES. 

 BY THEODORE HUBENER. 



HPHE velocity of the flow of solutions in capillary tubes appears 

 -*- not to depend solely on their weight and capillary adhesion. 

 Poiseuille has demonstrated that the velocity of flow of a mixture of 

 water and alcohol decreases in proportion as the specific gravity 

 increases by the addition of larger and larger quantities of water, 

 to a minimum which corresponds exactly to the maximum of con- 

 traction of the mixture. Girard found that the velocity of flow of 

 chloride of sodium is less than than that of a solution of chloride 

 of potassium of the same density. 



M. Hiibener thought that, beside the adhesion and the weight of 

 the liquid, an important factor for the velocity of flow of a solution 

 must be the intermolecular friction resulting from its greater or 

 less cohesion ; and to test this he has compared the velocities of a 

 number of solutions of very different chemical compositions brought 

 to the same density. 



The liquid was introduced into a vertical rectilinear glass tube of 

 50 centims. length and 1*78 centim. diameter, having a capillary 

 continuation of about 40 centims. length. The large tube presented 

 two marks ; and with a seconds-watch the time was accurately 

 measured which was required for the level of the liquid to fall from 

 one of these marks to the other. 



Operating in this way upon solutions of chloride, bromide, and 

 iodide of potassium, of chloride of sodium and of ammonium, with 

 a density of 1'059 and at a fixed temperature, the author ascertained 

 that the velocity ofjloiv of saline solutions is as much lower as the 

 atomic weight of the salt dissolved is less. For the different binary 

 bodies above indicated, it is the metal which has the greatest influence 

 upon the velocity of flow, much more than the metalloid. The va- 

 riations presented by the velocity from one body to another are as 

 much more marked as the tube is more capillary and as the con- 

 centration of the solution is greater. 



On comparing two solutions, of chloride of sodium and potassium. 

 at 1 - 1058 density, the author arrived at the remarkable result that 

 the times of flow of these two salts are found to be very sensibly 

 proportional to their equivalents. From this experiment, and from 

 others analogous, extended also to the chlorides of the alkaline-earthy 

 metals barium, strontium, magnesium, M. Hiibener thinks it may be 

 concluded generally with a high degree of probability, that the velo- 

 cities of flow of these bodies in solution in water, to a certain degree of 

 concentration, are in the same ratio as their equivalents. 



The explanation of these facts is, according to M. Hiibener, 

 to be found in the circumstance that the molecules of substances 

 which have a higher equivalent are larger, but, on the other hand, 

 in less number, and consequently must give rise to less friction 

 with the solvent in which they are held, thus communicating greater 



