426 RECORD OF SCIENCE FOR 1887 AND 1888. 



atomic weights from their relative densities. Scott, iu his experiments, 

 has paid especial attention to the following points: 



(1) The preparation of purer gases. 



(2) The use of larger volumes. 



(3) The measurement of both gases in the same vessel. 



(4) The analysis of the residue left after explosion of the mixed 

 gases, and determination of the impurity in each experiment. 



Twenty-one experiments were made, giving as the most probable ratio 

 1.994 volumes of H to one volume of O. Hence, if the density of O iu 

 terms of H is l.'5.9627, its atomic weight becomes 16.01. (Proc. Roy. 

 Soc, XLii, 396. Chem. News, LVi, 173.) 



Morley's paper (Am. Chem. Journ., x, 21) is essentially a discussion 

 of Scott's work, with an outline of proposed methods for the settlement 

 of the problems under consideration. 



Lord Eayleigh (Chem. News, lvii, 73) has re-determined the density 

 ratio between H and O, and finds it to be 1: 15.884. The application of 

 this ratio to atomic- weight discussions depends upon investigations like 

 those of Scott. Eayleigh also calls attention to a source of error iu the 

 process of weighing gases, which arises from the fact that a glass globe 

 when exhausted of air, is sensibly condensed by atmospheric pressure ; 

 that is, its capacity when empty is perceptibly less than when full. 

 This error affects Eegnault's density determinations. Cooke and Eich- 

 ards (Am. Chem. Journ. x, 191) recognize the importance of Eayleigh's 

 observations, and apply them to the correction of their own results. 

 They determine the magnitude of the error produced in their own glass 

 globes, and flnd that it reduces their value for the atomic weight of 

 oxygen from 15.953 to 15.869. This is the lowest value yet assigned to 

 that constant. 



Keiser attempts to ascertain the composition of water directly by 

 weighing hydrogen occluded in palladium, expelling it by heat, burn- 

 ing it over copper oxide, and weighing the water so formed. Three pre- 

 liminary experiments (Berichte, xx, 2323) gave in sum a value for oxygen 

 of 15.8722. In a later i)a;per he gives in detail his process, together 

 with his final results. Ten combustions were made, with 6.5588 grammes 

 of hydrogen in all, giving values for O ranging from 15.943 to 15.958, or, 

 in sum, 15.9482. He shows that the hydrogen weighed was presumably 

 pure, and that no nitrogen was occluded with it. His final figure agrees 

 quite nearly with the earlier determination of Cooke and Eichards. 

 (Am. Chem. Journ., x, 249.) 



Fluorine. — The atomic weight of this element, which has hitherto been 

 determined by the conversion of fluorides into sulphates, Christenson 

 has verified by a new method. When the double fluoride of ammonium 

 and manganese, Am>MnF-,, is added to a mixture of potassium iodide 

 and hydrochloric acid, it liberates iodine, which may be titrated with 

 sodium thiosulphate. One molecule of the salt, as Above formulated, 

 sets free one atom of iodine. Four determinations were made, giving 



