CHEMISTRY

Preparation of Uranium

M. PELIGOT has communicated to the Annales de Chimie et de Physique [XVII. 368] a short note on the preparation of uranium. A mixture of 75 grazes of uranous chloride, 150 grazes of dry potassium chloride, and 50 grazes of sodium in fragments, is introduced into a porcelain crucible, itself surrounded by a plumbago crucible. The reaction is effected in a wind furnace, at the temperature of redness, but the heat must be increased for a short time at the close of the operation. In the black slag may be found, after cooling, globules of fused uranium. Throughout the operation, it is necessary to avoid the presence both of moisture and atmospheric air.

A specimen of the metal prepared in this way by M. Valenciennes had the specific gravity, 18.33. Uranium, is, therefore, one of the densest of metals.

Stannous Chloride and Acids of Arsenic

BETTENDORFF has examined the action of stannous chloride on the oxygen acids of arsenic. When a solution of stannous chloride in fuming hydrochloric acid is added to a solution of arsenious or arsenic oxide in the same acid, a brown precipitate is formed, which, after proper washing and drying, consists of metallic arsenic mixed with a small quantity of stannic oxide. In an aqueous solution of arsenious or arsenic acid, stannous chloride produces no precipitate; but on adding strong hydrochloric acid till the liquid fumes slightly, precipitation takes place. Arseniferous hydrochloric acid of sp. gr. 1.182 to 1.135 gives an immediate precipitate; the same diluted to sp. gr. 1.115 gives imperfect precipitation after some time; and in a similar solution of sp. gr. 1.100, no precipitation takes place. From this it may be inferred that the reaction occurs only between stannous chloride and arsenious chloride; further, that in a solution of arsenious acid in hydrochloric acid of sp. gr. 1.115 part of the arsenic is present as chloride, but that hydrochloric acid of sp. gr. 1.100 dissolves arsenious acid as such, without converting it into chloride. The reaction above described is extremely delicate, and capable of detecting 1 pt. of arsenic in a million parts of solution. On antimony compounds stannous chloride exerts no reducing action, even after prolonged heating: hence the abovedescribed reaction may be used to detect the presence of arsenic in antimony compounds, the solution being previously saturated with hydrochloric acid gas. Another useful application of the same reaction is to the preparation of hydrochloric acid free from arsenic: 421 grms. of crude hydrochloric acid of sp. gr. 1.164 were mixed with a fuming solution of stannous chloride, the precipitate separated by filtration after twenty-four hours, and the hydrochloric acid distilled, the receiver being changed after the first tenth had passed over, and the remaining liquid distilled nearly to dryness. The acid thus obtained gave not the slightest indications of arsenic, either by Marsh's test or by precipitation with hydrogen sulphide.-[Zeitschr. f. Chem. (2), v. 492.]

Dichlorinated Aldehyde

PATERNO has obtained dichlorinated aldehyde C₂H₂Cl₂O by the action of sulphuric acid on dichloracetal. It is a liquid boiling at 89fl-90a, attracts moisture from the air, and is thereby converted into a hydrate, which crystallises in beautiful laminae, Left to itself, even in sealed tubes, it becomes dense, and changes into a white amorphous mass, which has the aspect of porcelain; but, when heated to 120a, is reconverted into the original product. Dichlorinated aldehyde dissolves without decomposition in alcohol and ether; when poured into water, it first sinks to the bottom and then dissolves, especially on application of heat; in short, it exhibits the most complete analogy with chloral. It is difficult to oxidise, its vapour not undergoing any sensible alteration when mixed with air or oxygen and passed over red-hot spongy platinum; but when gently heated with several times its own volume of fuming nitric acid, it is energetically attacked and converted into dichloracetic acid C₂H₂Cl₂0₂. Phosphoric pentachloride attacks it strongly, producing the compound C₄H₄Cl₆O or C₂H₂Cl₂O. C₂H₂Cl₄, the action doubtless consisting in the replacement of O by Cl₂ (as in the action of PCl₅ on aldehydes in general), whereby C₂H₂Cl₄ is produced, which, as soon as it is formed, unites with a portion of the undecomposed dichlorinated aldehyde, producing the compound C₄H₄Cl₆O. The constitution of this body may be represented by the following formulae:

CHCl₂-CH₂-O-CCl₂-CHCl₂

or perhaps by

CHC1₂-CHCl-O-CHCl-CHC1₂.

The compound C₄H₄Cl₆O is a colourless oil, having an irritating odour, heavier than water, soluble in alcohol and ether; it distils at 2508 emitting acid vapours. Alcoholic potash attacks it strongly, with evolution of heat, and formation of potassium chloride; and, on adding water to the resulting liquid, a heavy aromatic oil separates, boiling at 196l, and having the composition C₄H₄Cl₄0-that is to say, containing 2HCl less than the preceding. This last compound unites directly with four atoms of bromine, forming the crystalline compound C₄H₂Cl₄Br₄O. In this respect, the compound C₄H₂Cl₄O is analogous to Malaguti's chloroxethose C₄H₆O, which he obtained by abstracting four atoms of chlorine from perchlorinated ethylic oxide C₄H₄Cl₆O may be designated as hexchlorinated ethylic oxide, and C₄H₂Cl₄Br₄O as tetrachloro-tetrabrominated ethylic oxide. The two compounds C₄Cl₆O and C₄H₂Cl₄O may also be regarded, respectively, as perchlorinated vinyl oxide and tetrachlorinated vinyl oxide.[Giornale di Scienze di Palermo, v. 123, 127.]

Colouring Matter of wine

FR. PONCHIN proposes the use of a solution of potassium permanganate acidulated with sulphuric acid to distinguish between the natural colouring matter of wine and the various substances added to imitate that colour. For this purpose a normal solution of 2 grammes of the permanganate in 100 grammes

of distilled water is prepared when wanted for use; 15 grammes of this solution acidulated, and 3 drops of pure sulphuric acid, are added to 15 grammes of normal red wine contained in a test-tube, and the liquid after being shaken is left at rest. The greater part of the colouring matter is then slowly precipitated in red flocks, while the supernatant liquid retains the same colour, without weakening, for 24 hours afterwards. After a few days, however, the precipitate acquires a deeper red colour and the liquid becomes nearly colourless. For very deeply coloured wines a larger proportion of the normal solution must be used, care being, however, taken not to add it in excess, as that would produce a complete decolorisation. If, on the other hand, the same solution be added in the same quantities to wine which has been artificially coloured red, the deception will soon become apparent by the speedy decolorisation of the liquid, or by the communication of some different colour to the liquid and to the precipitate. The following table exhibits the various colours assumed by the liquid and precipitate produced under these circumstances in wine coloured by different substances

Dye-woods resist decolorisation more strongly than vegetable juices; and Brazil wood, when treated with the above-mentioned reagent, aided by heat, acquires a crimson-red colour, due to the formation of brazilin.-[Ann. di Chim. app. alla Med., September, 1869, p. 142.]