70 Scientific Intelligence. 



inula Pb(S0 4 )„. (H 2 0) 4 . Zinc and copper persulphates were also 

 produced as deliquescent crystalline needles. All attempts to 

 prepare sodium, lithium and magnesium persulphates were unsuc- 

 cessful owing apparently to their exceeding solubility. — J. Chem. 

 Soc, lix, V7l, October, 1891. G. f. b. 



3. On the Preservation of Sodium. — According to Rosen- 

 feld, when sodium which has been kept under mineral oil and is 

 covered with a crust, is immersed in a mixture of petroleum three 

 parts and amyl alcohol one part, or rubbed with a cloth soaked 

 with this mixture, it acquires at once a silvery luster. If now it 

 be put into petroleum containing 5 per cent amyl alcohol, then 

 washed with pure petroleum and kept in petroleum containing 

 one half to one per cent of amyl alcohol, it preserves this luster 

 for a long time ; becoming covered very slowly however with a 

 film of sodium-amyl oxide which is easily removed with filter 

 paper. Potassium and lithium can be purified similarly. Sodium 

 thus cleaned combines at once with mercury, evolving light. By 

 pressing clean sodium and potassium together under a mixture 

 of one part amyl alcohol and nine parts petroleum, the liquid 

 alloy of these metals is easily obtained. By mixing one gram of 

 the clean sodium rubbed to a fine powder with three grams of 

 salt, with 0*7 grams of sulphur, avoiding pressure, combination 

 takes place with the evolution of light and sodium sulphide is 

 formed. Selenium and tellurium behave similarly. — Ber. Bert. 



Chem. Ges., xxiv, 165« ; J. Chem, Soc., lx, 982, Sept. 1891. 



G. F. B. 



4. On New Oxygen Compounds of Molydenum and of Tung- 

 sten, — Pechaed has examined the yellow coloration produced 

 by the action of hydrogen peroxide upon molybdates and tung- 

 states, and concludes that it is due to higher oxygen compounds 

 of these metals. When potassium trimolybdate is treated with 

 hydrogen peroxide it dissolves forming an orange-yellow solution 

 which deposits on concentration yellow crystals apparently tri- 

 clinic, having the composition K 2 Mo 2 8 . (H 2 0) 4 . Heated gently 

 in a vacuum, the crystals lose water and oxygen and leave a 

 residue of acid potassium molybdate. The ammonium salt is 

 similarly prepared. Both salts are decomposed by alkalies with 

 evolution of oxygen. They evolve chlorine when treated with 

 hydrochloric acid and set free iodine from potassium iodide. In 

 the same way, sodium paratungstate boiled for a few minutes 

 with hydrogen peroxide becomes yellow in color and is no longer 

 precipitated by nitric acid. On evaporation the solution deposits 

 white crystals having the composition Na 2 W 2 8 . (H 2 0) 2 . The 

 above salts are regarded by the author as establishing the exist- 

 ence of per-molybdic and per-tungstic oxides Mo 2 0, and W 2 7 , as 

 well as the corresponding acids, H 2 Mo 2 8 and H 2 W 2 8 . — C. B.,, 

 cxii, 720, 1060 ; J. Chem. Soc., lx, 988,~Sept. 1891. g. f. b. 



