a 3 



SCIENCE. 



[N. S. Vol. XX. No. 496. 



evening, May 12, 1904, in the assembly hall of 

 the Cosmos Club. 



The first paper on the program, entitled 

 ' Heat of Dissociation Proportional to Atomic 

 Weight,' was presented by Dr. E. A. HiU. 

 The paper was a synopsis of the author's dis- 

 sertation presented to the Columbian Univer- 

 sity for the degree of doctor of philosophy. 

 . The second paper on the program, entitled 

 'The Colloid Theory of Plasticity,' was pre- 

 sented by Allerton S. Cushman. The speaker 

 reviewed briefly the evidence which has al- 

 ready been published by himself and other in- 

 vestigators, which tends to show that the two 

 important useful qualities of clays, viz., plas- 

 ticity and binding power, are caused by the 

 presence of a certain proportion of colloid 

 particles. To prove this, a large amount of 

 evidence has been collected and artificial clay 

 bodies have actually been synthetically pre- 

 pared in the laboratory, possessing all the pe- 

 culiar properties of natural clays. 



Experiments were made on the lecture table 

 which showed that the addition of certain re- 

 agents, such as tannic acid, alutm and am- 

 monia, to a pure kaolin clay profoundly modi- 

 fies the properties and the relation of the clay 

 body to water. Such reagents have no action 

 on inert crystalline particles, but they do upon 

 colloids, producing various effects, such as 

 coagulations, flocculations and deflocculations. 

 Curiously enough, all these reagents, as was 

 shown by a simple experiment, increase the 

 binding power of clay, either by deflocculation 

 of the colloids already present or by producing 

 reactions involving the formation of new col- 

 loids. Acheson has recently claimed and ob- 

 tained a patent for increasing the binding 

 power of clay by treatment with tannic acid. 

 This process is called the Egyptianizing of 

 clay on the, perhaps, somewhat fanciful theory 

 that it was the tannic acids of the straw in- 

 fusion rather than the fiber of the straw itself 

 which gave strength to the low binding clays 

 of ancient Egypt. Erom more recent work it 

 is questionable whether small amounts of am- 

 monia will not produce the desired effect even 

 better than tannic acid at a much less expense, 

 and in so simple a manner that its use can 

 not be restricted by patents. 



Eor the last fifty years occasional investi- 

 gators have been noticing that clays and soils 

 have the power of absorbing certain ingredi- 

 ents from solutions in which they are soaked, 

 and further, that these absorptions are se- 

 lective, certain substances being eagerly taken 

 up and others rejected. If the clay is first 

 heated to a certain point it no longer exhibits 

 this power, showing that it is not due to ad- 

 sorption on the particles. This again is a 

 colloid property, and inorganic colloid precipi- 

 tates made in the laboratory show the same 

 peculiarity. Clays that have been treated 

 with tannic acid and ammonia will absorb less 

 water than the untreated clays and will, there- 

 fore, require less water to bring them to a 

 desired consistency. Thus the danger of 

 shrinkage and cracking on drying out is less- 

 ened. Attention was called to the importance 

 of the study of these selective absorptions by 

 clay bodies in the investigations of soil 

 physics. 



The third paper on the program was en- 

 titled 'Notes on the Methods of Detection of 

 Sesame Oil,' and was presented by L. M. Tol- 

 man. A number of imported olive oils were 

 found by the author that gave a marked reac- 

 tion with the Baudouin or Villerecchia re- 

 agents. 



The substance in these oils giving this reac- 

 tion can be removed by alcohol so that the 

 purified oil gives no color with these reagents. 

 If Sesame oil is present the reaction is not 

 decreased by this method of purification. 



The fourth paper on the program, by Peter 

 Fireman and E. G. Portner, on ' Some Ob- 

 servations on the Dissociation of Chlorides by 

 Means of a Qualitative Test,' was presented 

 by Dr. Eireman. 



The last paper on the program for the even- 

 ing was a ' Note on a Bibliography of Solu- 

 bilities,' presented by A. Seidell. The author 

 mentioned that the preparation of a bibliog- 

 raphy of solutions had been begun about 

 eighteen years ago by a committee appointed 

 by the British Association for the Advance- 

 ment of Science. This committee reported 

 eight years later (1894) that they had col- 

 lected aU the references to work on solutions 

 published prior to 18Y4 in the periodicals cata- 



