Chemistry and Physics. 185 



SCIENTIFIC INTELLIGENCE 



I. Chemistry and Physics. 



1. The Question of Change in Total Weight of Chemically 

 Reacting Substances. — H. Landolt has devoted many years of 

 the most painstaking work in investigating the weights of sub- 

 stances in closed glass vessels before and after they were mixed 

 to produce chemical reactions. In 1893 he published his first 

 paper on the subject, in which he described work with reactions 

 between silver sulphate and ferrous sulphate, iodic acid and 

 hydriodic acid, iodine and sodium sulphite, and chloral hydrate 

 and alkali. As a result of these researches he was unable to 

 establish with certainty any change in the total weight, but it 

 appeared that the separation of silver and of iodine were accom- 

 panied by a slight loss in weight, so that the work was continued. 

 In 1896 results were described, obtained with a balance of great 

 precision, and with the use of much care, in which it was found 

 that a loss was indicated, where silver or iodine were set free, in 

 42 out of 54 separate experiments. The changes in weight 

 resulting from the use of 60 to 120 g. of reacting mass varied 

 usually between -003 and *050 mg., and were often less than the 

 estimated maximum error of *03 mg. At this time it appeared 

 to Landolt that these losses in weight, although small, were real, 

 and he suggested the view, which was supported by the doctrine 

 of the decomposition of radio-active atoms, that the violent shock 

 which the atoms receive in chemical reactions might possibly 

 cause the splitting off of minute particles of matter in the case of 

 elements not belonging to the radio-active class, and that these 

 might possess the property of penetrating the walls of glass ves- 

 sels. Landolt has now published the results of additional, very 

 elaborate, work on the same subject. He has explained fully 

 the cause of former losses in weight in the fact that glass vessels 

 which have been slightly heated by the chemical reaction within 

 often do not return to their proper weight until after the lapse of 

 a week or more, and he reaches the conclusion that in all of the 

 15 chemical reactions studied by him, no change in the total 

 weight of the reacting substances has been established. This 

 conclusion is of much importance in deciding the question, 

 whether or not the atomic weights are of constant magnitude, for 

 there appears to be no doubt that the force of gravity acts upon 

 an atom to the same extent in any state of combination. — 

 Zeitschr. physikal. Chem., lxiv, 581. h. l. w. 



2. The Volume of Radium Emanation. — Professor Ruther- 

 ford has recently made some measurements of the volume of the 

 gaseous emanation produced by radium. For this work the 

 Royal Academy of Science in Vienna put at his disposal a prepa- 

 ration containing about 250 mg. of pure radium. Much diffi- 



