62 Scientific Intelligence. 



publications which has appeared in recent times. We think the 

 time has come however for using the terms " atomic mass " and 

 " molecular mass " in place of atomic weight and molecular 

 weight. It would accord with present practice too, if den- 

 sity were given in absolute measure instead of being referred to 

 the air standard. The translation is one of rare excellence and 

 Dr. Bedson and Mr. Williams deserve the thanks of English- 

 speaking chemists not only for producing Dr. Lothar Meyer's 

 book in its English dress but for presenting it in so acceptable a 

 form. The mechanical execution of the book is excellent. 



G. F. B. 



2. On an Experiment to illustrate Valence. — Lepsius has con- 

 trived a lecture apparatus for demonstrating the valence of the 

 metals, based upon the method adopted by Nilson and Petterson 

 to determine the atomic weights of the rare elements ; i. e., heat- 

 ing a weighed quantity of the metal in dry hydrogen chloride gas 

 and measuring the hydrogen set free. In a combustion tube 40 cm . 

 long, pieces of thallium, of zinc and of aluminum are placed, about 

 10 cm apart; the weight in each case corresponding to double the 

 atomic weight in milligrams; i. e., 408 mgrms thallium, ii3 mgrms 

 zinc and 54 m?rms aluminum. The hydrogen chloride is evolved 

 by the action of strong sulphuric acid on a piece of ammon- 

 ium chloride and is carefully dried by passing it through 

 sulphuric acid. The hydrogen is collected in an apparatus like a 

 Hofmann apparatus for decomposing water, but which has three 

 graduated tubes, the whole rotating in a socket containing mer- 

 cury so that the gas may be sent into either of the tubes at will. 

 The three tubes are filled with a dilute soda solution. In perform- 

 ing the experiment the thallium is first heated with a Bunsen 

 burner and the hydrogen collected in one of the three tubes. Then 

 the zinc is similarly heated and after that the aluminum, the evolved 

 gas being collected in the second and third tubes. The hydrogen 

 in the first tube will occupy 22 # 32 cc , that in the second 44*62 cc , and 

 that in the third 67*86 cc ; the ratio of the three being 1 : 2 : 3, or 

 that of the valence of the metals used. — Ber. Berl. Chem. Ges., 

 xxi, 552-561, Feb., 1888. G. f. b. 



3. On the action of Hydrogen sulphide on Arsenic acid. — The 

 action of hydrogen sulphide on arsenic acid has been studied by 

 Braxxee and Tomicek. They conclude: 1st, that, other things 

 being equal, more arsenic pentasulphide is formed (a) the larger 

 the quantity of hydrochloric acid present, (b) the larger the quan- 

 tity of hydrogen sulphide put into the solution in a unit of time, 

 and (c) the lower the temperature (between 0° and 100°); and 2d, 

 that, in consequence of the reducing action of the hydrogen sul- 

 phide, more arsenic trioxide is formed (a) the less hydrochloric acid 

 there is present, (b) the smaller the quantity of hydrogen sulphide 

 and (c) the higher the temperature. Hence when a rapid current 

 of hydrogen sulphide is passed into a solution of arsenic acid arsenic 

 pentasulphide alone is formed, though but slowly if free hydro- 

 chloric acid is present and the liquid is kept warm. — J. Chem. 

 Soc, liii, 145-159, Feb., 1888. G. f. b. 



