313. Sulphide of Hydrogen in Blowpipe Analysis. The characteristic sulphide precipitates of the metals are obtained in blowpipe analysis by the following process, communicated to the Chemical Society of Berlin, by Mr. J. Landauer. The metallic compound is mixed with powdered hyposulphite of soda, and brought with a borax bead into the reducing flame; on cooling, the bead presents the sulphide coloration of the metal present. Volatile compounds are to be treated in tubes

314. Bromine in Analysis.-Waage agrees with Kammerer, in recommending bromine (in aqueous or hydrochloric acid solution) as a substitute for chlorine in analysis. Such bromine water has been employed with most satisfactory results for the oxidation of sulphur and metallic sulphides.

315. Bubbles of Air in Fluids. The separation of gas dissolved in a liquid by the introduction of various substances, is explained by the hypothesis of the action of minute particles of dust or dirt on the substances, which serve as nuclei, or points of escape for the gas. Mr. Charles Tomlinson thinks that the separation is owing to the presence of a film of oil or grease to which a gas or vapor will adhere, while water will not. Such a surface consequently attracts the gas, and the moment it is set free, it has a tendency to escape. In support of this hypothesis, Mr. Tomlinson shows that if a chemically clean glass rod is immersed in a saturated solution of a gas, not a bubble escapes, because both gas and fluid are equally attracted, whereas, if it is soiled to the slightest extent, the gas at once escapes freely. In the same manner a flint pebble that has been handled is covered with bubbles the moment it is placed in a solution of a gas, while, if it is broken, and a clean surface thus obtained, no gas appears on the clean or fractured surface when it is immersed. The permanent nuclei, such as charcoal, Mr. Tomlinson thinks, act on Saussure's principle of the absorption of gases and

vapors.

316. Hydrogen Flame Tests.-Mr. W. F. Barrett, by a very

interesting series of experiments, arrives at the following conclusions regarding such flames:

1. The combustion of hydrogen exhibits some physical peculiarities, and produces phosphorescence in many substances with which it comes in contact.

2. The blueness so often seen in a hydrogen flame is due to the presence of sulphur, derived either from the vulcanized rubber tubing, or from atmospheric dust, or from the decomposition of the sulphuric acid spray from the generator.

3. A flame of hydrogen forms an exceedingly delicate reagent for the detection of sulphur or phosphorus, and possibly also of tin.

4. Many sulphates, and also carbonic acid, are apparently decomposed by a hydrogen flame.

The third result Mr. Barrett supposes may be of some practical use in the detection of sulphur and phosphorus in the iron manufacture, and the fourth he thinks may be practically applied as a test of the air in theatres and other crowded buildings.

317. Quantitative Determination of Arsenic.-Prof. J. C. Draper describes in the American Chemist a new process for the quantitative determination of arsenic in cases of poisoning by this drug. Its peculiarity consists in the precipitation of the metal from the arsenide of hydrogen by red-hot platinum.

318. Magnesium in Marsh's Test.-Magnesium may be substituted for zinc in Marsh's test, by using a (u) tube for the decomposition apparatus. The bend of the tube is filled with pure mercury through which the magnesium strip or wire is passed into the acid solution. The mercury acting like a valve enables the operator to keep the rate of evolution of the gas completely under control.-(PROF. J. C. DRAPER, in the Scientific American.)

319. Action of Dextrine on the Iodine Starch Test.O. Knab finds that dextrine annulls the well-known reaction of iodine and starch; it will even decolorize a mixture in which the blue reaction has already been obtained.

320. Care in Filtration.-In the filtration of certain substances, as the dilute aqueous solution of the cheesy chloride of silver, and also of albumenoid bodies, the beak of the funnel must touch the side of the vessel that receives the filtrate, in order that the liquid may reach the bottom of the vessel without being subjected to a shock. The influence of the agitation produced by permitting the drops to fall from the beak of the funnel into the liquid is often sufficient to change the substance in solution from the soluble to the insoluble state.

321. Precipitation of Uric Acid.-Salkowski has shown that hydrochloric acid does not precipitate the whole of the uric acid from urine; he therefore proposes to precipitate the rest of the uric acid by silver nitrate.

322. Solubility of Chloride of Silver.-M. J. S. Stas shows that the chloride of silver is not always insoluble, as is generally supposed, but that its solubility varies with its physical condition, and also with the temperature. The chloride of silver, he says, exists in various forms, viz., (a) gelatinous; (b) flocculent or cheesy; (c) pulverulent; and (d) granular, scaly, crystalline, or melted. In the granular, scaly, or crystalline state, at the ordinary temperature, it is almost insoluble, though in boiling water it dissolves to a slight extent; of the other forms, a, b, c, the cheesy form is the most soluble, though the degree of solubility diminishes with the contraction of

the masses.

323. Test for Alcohol.-M. Berthelot recommends chloride of benzoyl as a test for traces of alcohol in water; benzoic ether being formed.

324. Saccharimetry. A new system of saccharimetry may be founded on the contraction a solution of cane-sugar undergoes at the moment of inversion.-(M. G. CHANCEL.)

325. Decomposition of Iron. Meineke proposes the substitution of ferric chloride for cupric chloride in Gintl's method for the decomposition of iron.

GEOLOGY.

MINERALOGY.

326. Diamonds in South America. In his description of the region in which these diamonds are found, Dr. Shaw states that the diamonds originally belonged to some metamorphic rock, probably a talcose slate, which occupied the heights during the upheaval of the trap which has given to the country its physical features. This upheaval was followed by a period of lakes, the traces of which still exist, and it is in the soil of these dried-up lakes that the diamonds are found.

Professor T. R. Jones, on the contrary, thinks that the diamonds are supplied both from metamorphic and igneous rocks, and that the gravel in which they are found has been conveyed by glacial action from very remote mountains.

Microscopic diamonds have been found in xanthophillite. 327. Peat Deposits. The great depth of peat deposits is the result of the gradual filling up by vegetable growths of the outlet of the pond or marsh in which the peat is produced. The growth consequently takes place on the surface, and is only to be limited by the height from which the supply of water is derived.

328. Origin of Mineral Veins. J. Arthur Phillips closes á paper on the origin of mineral veins with the following summary:

1. Metalliferous lodes are more numerous and productive in the vicinity of igneous rocks than elsewhere.

2. There is abundant evidence of volcanic eruptions having taken place during all periods of geological time.

3. Solfatara action and thermal springs are often the latest evidence of volcanic disturbance.

4. Crystalline quartz, iron pyrites, mercury sulphide, and various other minerals, are at the present time being deposited by solfatara action in veins possessing many of the characteristics of ordinary lodes.

gas

329. The Lava of Vesuvius.—The condition of the lava of the recent eruption, is thus described by a writer in Nature: At first, the whole surface of the lava-streams seems to exhale steam and hydrochloric acid, and the atmosphere is filled with a disagreeable odor which makes breathing uncomfortable. But very quickly the exhalations are localized around the little centres of fire, whose activity continues for many months, and the emanations from which are gradually modified. Thus, as seen from Naples at the time of the visit, the whole of the lava appeared to be smoking, and it was possible clearly to distinguish the tracks of the whitish vapors which wandered over the surface; but close at hand there was nothing to be seen but the fumaroles, between each of which there is plenty of space. The and the hot vapors which the lava emits are charged with numerous substances, and become the source of mineral deposits, which fill the tourist with wonder. One of the most curious phenomena observed is the power of the burning lava to retain an enormous quantity of water and salt, which it does not allow to escape until it begins to cool. The formation of salt is shown generally over the whole stretch of lava emitted in 1872. Soon after the surface cools it is covered with a light crust of salt, which forms in similar flowery patterns on the beds of cinders that cover the plains, the cinders themselves emitting hydrochloric acid everywhere. The first showers of rain caused this deposit to disappear rapidly; and there remained on the 12th of May only scanty traces, except on the lower surface of the blocks, where the rain had not the power to