THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES. ] 



Art. XXYII. — The Compressibility of Colloids, with Appli- 

 cations to the Jelly Theory of the Ether ; by C. Barus. 



1. Colloids in view of their varied and frequently anoma- 

 lous physical properties,* not to mention their tremendous 

 biological importance, offer a fascinating field of research. I 

 have, however, undertaken the present experiments rather 

 with ulterior motives, because of their bearing on the elastic 

 propertiesf of glass, geologically considered. Apart from this, 

 certain practical difficulties have presented themselves in the 

 course of my work for which I hope the present paper will 

 suggest a remedy. Thus, in endeavoring to ascertain the effect 

 of pressure on solution,^: I was invariably confronted by the 

 difficulty that the solute precipitated by pressure collects at 

 the bottom of the piezometer tube, is segregated from the 

 bulk of the solvent and therefore no longer in place for solu- 

 tion on removal of pressure. Methods which work faultlessly 

 for fusion are thus apt to fail when applied to solution. Now 

 if it can be shown that the physical properties of a solution 

 vary but slightly in presence of a colloid, that the former may 

 be made viscous enough to retain the precipitate in place dur- 

 ing compression, I see no reason why the fusion methods are 

 not adapted for the study of solutions. 



A final inquiry of great interest is the compressibility of 

 well coagulated colloids, seeing that compression is apt to be 

 accompanied by the breakdown of stress in a solid medium. 

 Indeed I here encountered some astonishing phenomena, and a 



* On analogies in the thermal behavior of india rubber jelly, muscular tissue, 

 etc., see Bjerken, Wied. Ann., xliii, p. 817, 1891. 

 f See my paper in this Journal, xli, p. 110, 1891. 

 X Bulletin U. S. Weather Bureau, No. 12, p. 18 et seq., 1895. 



Am. Jour. Sci.— Fourth Series, Vol. YI, No. 34.— October, 1898. 

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