Chemistry and Physics. 225 



scale, consisting of an upper fixed part graduated according to 

 the tangent of the deflection-angles, and of a lower part placed 

 behind the former and movable vertically. If one of the two 

 equilibrated globes be exhausted, or if, what is the same thing, 

 the weight of air which it contains be calculated from its capa- 

 city and this weight be added to the globe full of air, a deflection- 

 angle will be obtained whose tangent is proportional to this ex- 

 cess of weight. If now the same globe be filled with a given gas, 

 a second deflection-angle will be obtained whose tangent will be 

 proportional to the algebraic sum of the weight of the air and 

 the excess of weight of the gas. Hence, the tangent of the sum 

 of the two deflection-angles is proportional to the weight of the 

 gas. It is necessary, therefore, only to divide this tangent into 

 as many parts as there are units in the molecular weight of the 

 gas employed. The movable scale can therefore be empirically 

 adjusted either with a pure gas or by means of the corresponding 

 •weight. Since, however, the sum of the deflection-angles is a 

 function of the temperature and pressure, it is necessary of course 

 to adjust the movable part of the scale for the given conditions. 

 — Ber. Bert. Chem. Ges., xx, 1433, May, 1887. ' g. f. b. 



4. On the Evolution of Sulphurous oxide and of Oxygen in 

 KippPs Apparatus. — Neumann has extended the use of Kipp's 

 apparatus for the ready evolution of gases, first suggested by 

 Winkler for chlorine. For sulphurous oxide, he proposes a mix- 

 ture of three parts calcium sulphite and one of gypsum made into 

 cubes, as in Winkler's method. These cubes are placed in the 

 middle bulb of an ordinary Kipp's apparatus and crude concen- 

 trated sulphuric acid is made to act on them. Half a kilogram 

 of cubes yielded the author a constant current of gas for thirty 

 hours. They remained unaltered in shape, no gypsum falling to 

 the bottom of the vessel. It is desirable to moisten no more of 

 the cubes than is necessary to produce the amount of gas re- 

 quired. The evolution of oxygen in this way is effected by the 

 use of cubes made of a mixture of two parts barium peroxide, one 

 jiart manganese peroxide and one part gypsum. The evolution 

 of the oxygen is produced by means of hydrogen chloride solution 

 of a specific gravity of 1*12 diluted with an equal quantity of 

 water. In the reaction there is evolved beside the oxygen a little 

 chlorine ; and hence it is necessary to wash the gas in an alkali 

 solution, as is the case with the oxygen which is evolved by heat- 

 ing potassium chlorate. — Ber. Berl. Chem. Ges., xx, 1584, June, 

 1887. G. F. B. 



5. On the Vapor-density of Tellurium tetrachloride and on the 

 Valence of Tellurium. — Of the elements of the sulphur group, no 

 compounds are known, permanent in the state of vapor, in which 

 for each atom of the element there are more than two of a univa- 

 lent radical. The compounds SC1 4 , SeCl 4 and TeCl 4 are known, 

 it is true, but the first is permanent even in the liquid state, only 

 at —21°, and the second decomposes at 218°, yielding a vapor 

 desity of 3'922 instead of 7*63; being broken up into selenium 



Am. Jour. Sci.— Third Series, Vol. XXXIY, No. 201.— Sept., 1887. 

 15 



