222 Scientific Intelligence. 



water-bath, its contents are evaporated to dryness, and then evap- 

 orated two or three times after the addition of a few cubic centi- 

 meters of hydrochloric acid, in order to remove nitric acid. The 

 precipitation and weighing of barium sulphate is then carried out 

 in the usual way. The author has determined sulphur in gun- 

 powder very satisfactorily by this method. — Comptes Mendus, 

 cxliii, 1160. h. l. w. 



3. The Detection of Traces of Zinc. — Bertrand and Javillier 

 have found that when ammoniacal solutions containing calcium 

 and small quantities of zinc are boiled until the ammonia is re- 

 moved, a precipitate consisting of calcium zincate, CaZn~„0 3 .oH 2 0, 

 is produced, and they have applied the reaction to the detection 

 of zinc when small quantities are present. For example, in 

 examining half a liter of water containing less than "001 s of zinc, 

 a little dilute milk of lime, or about 50 cc of lime water, is added, 

 and then 10 or 15 per cent of concentrated ammonia. The liquid 

 is then filtered if necessary, and is boiled as long as alkaline 

 vapors are evolved. After cooling, the precipitate of calcium 

 zincate, which is contaminated with calcium carbonate, is col- 

 lected on a small filter. The precipitate is dissolved in hydro- 

 chloric acid, the solution is evaporated to dryness to remove the 

 acid, and after taking up in water, the calcium is precipitated as 

 oxalate in presence of strong ammonia. The zinc remains in 

 solution, and by evaporating and calcining in the presence of sul- 

 phuric acid, it is converted into sulphate which can be weighed. 

 By dissolving the sulphate in one or two cubic centimeters of 

 water, testing one half with hydrogen sulphide and the other 

 half with potassium ferrocyanide, the presence of zinc may be 

 shown by the characteristic, white precipitates produced. Test 

 analyses made in the presence of - 001 to '01 s of zinc gave satis- 

 factory quantitative results, while as little as '0001 s in 100 cc of 

 water, one part in five million, was detected qualitatively. — 

 Comptes Renclus, cxliii, 900. h. l. w. 



4. Compounds of Ferrous Salts with Nitric Oxide. — Manchot 

 and Zechentmeter have made a study of the absorption of the 

 gas NO by solutions of ferrous salts. This is an interesting sub- 

 ject on account of the production of one of these black com- 

 pounds in the well known qualitative test for nitrates. Their 

 experiments were made by determining the volume of the gas 

 absorbed by solutions of ferrous salts at varying pressures. The 

 limit reached at pressures of about 2000 mm of mercury and at tem- 

 peratures near 0° corresponded to one molecule of NO to one atom 

 of iron. Experiments made at gradually increasing temperatures 

 did not show any sudden decrease in the amount of gas absorbed, 

 so that it does not appear probable that any compound with a 

 smaller proportion of nitric oxide exists, as has been supposed to 

 be the case by previous investigators. The authors did not suc- 

 ceed in obtaining the pure solid compounds, and they doubt the 

 purity of those previously described. — Ann. d. Chern., cccxl, 368. 



H. L. W. 



