July 1, 1921] 



SCIENCE 



17 



silver. This theory can account for the failure of 

 the reciprocity law, for the shape of the H and D 

 curve, for the phenomenon of reversal, and states 

 the distinction between the latent image and the 

 print-out image. The energy relationships are such 

 as to indicate the formation of a considerable pro- 

 portion of silver amide acid compound, which 

 then becomes the material affected by the de- 

 veloper. 



The interaction of platinum hydrogen acid and 

 hydrogen peroxide: S. A. Braley and O. V. 

 Shaffer. Following the work of Rudnick in 1917 

 a study of the preparation of HjPtClo was made. 

 It was found that commercial 3 per cent. H^O, 

 acted only very slowly on ignited platinum black, 

 and on platinum sponge did not give HjPtCl, suit- 

 able for accurate analytical work. By concen- 

 trating to about 30 per cent, and redistilling from 

 quartz to quartz HjOj was prepared which would 

 give acid with a KCl factor of .3045 and suitable 

 for accurate KCl determinations. 



7s there a sharp transition point ietweeii the 

 gel and sol? Eugene C. Bingham. The viscom- 

 eter gives a satisfactory method for distinguish- 

 ing sharply between a liquid and a solid. Under 

 the influence of a small shearing stress a liquid 

 is continuously deformed, whereas a solid is not. 

 The fluidities of a 10 per cent, gelatine sol in 

 glycerol-water mixture of 1.175 sp. gr. calculated 

 from the data of Arisz follow the equation 



= 0.000227 (« — 45.2) 



very closely. This indicates that the fluidity would 

 reach the zero value -when the temperature becomes 

 45.2° C. At this point the substance would be- 

 come a solid and there would appear to be a sharp 

 transition point between the two states. 



The validity of the additive fluidity formula: 

 Eugene C. Bingham and Belbert F. Brown. It 

 is shown that in many mixtures of inert liquids 

 there is a contraction of liquid in mixing. If this 

 contraction is multiplied by a constant, which is 

 usually about 2,000, one obtains the amount by 

 which the observed fluidity differs from the value 

 calculated on the additive formula. It is evident 

 from the above that even in the case of so-called 

 inert liquids there is an adjustment of the free 

 volume, for which several equations have been pro- 

 posed. These give as good agreement as can be 

 expected with the data available. 



The emulsion colloids as plastic substances: 

 Eugene C. Bingham and William L. Hyden. 

 The fluidity-volume concentration curves of sus- 



pension colloids were found to be linear by Bing- 

 ham and Durham, and the zero of fluidity served 

 to demarcate between the viscous liquid and plastic 

 solid. Nitrocellulose solutions in acetone present 

 a new case, differing from all others studied up to 

 the present. The fluidity of even very dilute solu- 

 tions is not a constant but a function of the 

 pressure. The solutions, therefore, act as plastic 

 solids even in very dilute solutions. It is found 

 to be convenient to measure the plasticity of such 

 solutions ill the viscometer. This has heretofore 

 always been done on the plastometer. 



The properties of cutting fluids: Eugene C. 

 Bingham. In cutting metals, fluids are often 

 used, sometimes to lower the temperature, often 

 to lubricate the surfaces between the tool and the 

 chip. But whereas lubrication \inder the best 

 conditions is merely a matter of viscosity, two 

 oils of the same viscosity may have the most ex- 

 traordinary difference in eflieieney. The cutting 

 oil par excellence is lard oil and it derives its 

 superiority from its high adhesion. Mineral oils 

 may have their lubricating eflieieney raised by 

 the addition of substances having high adhesion. 



The diffusion of hydrogen, through silica gluss: 

 John B. Ferguson and G. A. Williams. The 

 results of a redetermination of the rates at which 

 hydrogen will pass through silica glass at tempera- 

 tures between 440° and 727° C, and at pressures 

 between 0.5 and 1 atmosphere are herein presented. 

 The fact that helium will pass through siliea glass 

 at a much faster rate than does hydrogen has been 

 confirmed. 



The atomic iveight of nitrogen iy the thermal 

 decomposition of silver trinitride: Harold S. 

 Booth. In this determination silver trinitride was 

 slowly decomposed by heat in a suitable all-glass 

 apparatus into silver and nitrogen, the evolved 

 nitrogen passed through phosphorus pentoxide to 

 absorb the traces of moisture retained in the 

 interstices of the silver trinitride, and the nitro- 

 gen adsorbed in a charcoal tube immersed in 

 liquid air. The method as planned involved no 

 corrections except for errors in the weights. Every 

 precaution was taken to insure the purity of the 

 materials and the accuracy of the method. The 

 average of fourteen determinations of the ratio 

 3N : Ag gave 14.007 for the atomic weight of 

 nitrogen. 



Studies in adsorption from solution : W. A. 

 Patrick and D. C. Jones. A study of adsorption 

 in the capillaries of silica gelatine of a large num- 

 ber of two component systems has been partially 



