288 Intelligence and Miscellaneous Articles. 



with it on the velocity of fowling-piece shot of various sizes with 

 various charges of powder. The degree of uniformity of rate of 

 rotation of the cylinder is shown to be immaterial, and further it 

 is shown that no correction is needed for the weight of the tracing- 

 style nor for its scrape on the paper. With an A fork with 440 

 vibrations per second, it is stated that the number of vibrations 

 can be determined by this method to at least T -J^- of a vibration, and 

 the time-record consequently to -^j^-q of a second. — Silliman's 

 American Journal, December 1885. 



ON THE PERMEABILITY OF VARIOUS DIAPHRAGMS. 

 BY A. ZOTT. 



The chief results of a long investigation on this subject are 

 summed up by the author as follows : — 



1. The most useful diaphragm for dialytic separation is gold- 

 beater's skin. By its means twice as much, or in some cases, 

 according to the way in which the experiment is arranged, a far 

 greater separation is effected than with a dialysis of parchment 

 paper, which it exceeds in homogeneity and in its capacity to hold 

 water. 



2. For mixtures of liquids which would attack organic dia- 

 phragms, ordinary porous cells are best ; the separation which they 

 effect is, however, 60 to 75 times less, that is to say slower, than 

 that produced by goldbeater's skin. 



3. All phenomena of diffusion are greatly increased when the 

 diaphragm is first evacuated ; the increase of volume of the solution 

 in the dialysis is, however, far more considerable than the increase 

 of the quantities of material which pass out ; and the latter depends 

 again on the relative velocity of diffusion of the substances in 

 question. The more rapidly a substance of itself passes through 

 a diaphragm, the more considerable is the acceleration which its 

 velocity of diffusion experiences by exhausting the diaphragm. 



4. The exhaustion of the diaphragm must from time to time be 

 renewed, and this is best done after each experiment. 



5. After previous exhaustion endosmosis takes place even with 

 those diaphragms and porous plates which previously showed no 

 increase in volume of the inner liquid. 



6. Even substances which diffuse slowly, or what are called 

 colloids, may bring about a considerable endosmosis, which, with a 

 correspondingly long time of diffusion, may even exceed that of 

 some crystals. Endosmosis is independent of the transit of the 

 substance in solution, that is of the exosmosis, and when there is 

 a mixture of solution in the dialyser, it does not differ much from 

 that which the dissolved substances would separately bring about. 



7. Solutions which contain two different substances may be 

 more easily and completely separated in the dialyser, the further 

 apart are the relative velocities of diffusion. 



8. A dialytic separation is the more rapidly effected the more 

 frequently the outer water is renewed. — Wiedemann's Annalen, 

 Eebruarv*1886. 



