are to be added. The whole is to be well stirred together until it cools; after which it is melted and applied with a brush to the paper, in quires, in the same way as in preparing the waxed paper so much used in Europe for wrapping various articles.

The Chemistry of taking out Iron-moulds. J. F. Brown. (Pharm. Journ., 3rd series, ii., 278.) Although the routine method of doing this is familiar to every chemist, the chemical reactions involved are by no means generally understood, and therefore a brief account of them may not be unacceptable.

My attention was first called to the subject while testing the comparative efficiency of three familiar solvents of ferric oxide, viz., hydrochloric acid, oxalic acid, and quadroxalate of potassium-the sal acetos.

I was surprised to find that the latter, which I had regarded as most eligible merely for its convenience in application, was superior also in solvent power. When hydrated peroxide of iron is treated with a strong hot solution of sal acetos, in the proportion of two equivalents of the latter to one of the former, carbon dioxide is copiously evolved, the oxide is dissolved, and at the same time chiefly, if not wholly, reduced to the ferrous state.

The resulting solution is yellowish-green in colour, yields a wellmarked precipitate with potassium ferridcyanide, and appears to contain ferrous oxalate and neutral potassium oxalate. The following is the equation:

Fe2 Og H2O + 2 KH C2 O. H2 C2 04. 2 H2 O

2

2

The same result followed when the oxide was acted upon by a strong solution of oxalic acid at a boiling heat, but less quickly; moreover the resulting solution was of a deep yellowish-brown colour, and contained more ferric salt.

Three equivalents of oxalic acid to one of oxide were employed, as in the following equation:

Knowing that a mixture of sal acetos and cream of tartar is sometimes sold as salt of lemons, I next tested the solvent power of this combination.

Taking as my guide the proportions employed in making the ferrum tartaratum of the Pharmacopoeia, I compared the action on ferric oxide, of boiling solutions of acid tartrate of potassium, sal acetos, and of a mixture of the two.

Only a small portion of the oxide was taken up by the acid tartrate either alone or combined, and the equivalent quantity of ferric oxide was dissolved more rapidly by the sal acetos alone.

Experiments performed upon black oxide of manganese showed that it, like ferric hydrate, was dissolved by hot solutions of oxalic acid and sal acetos, but reprecipitated as flesh-coloured or buff manganous oxalate, carbon dioxide being given off; the following equations show the reactions :

Mn O2 + 2 H2 C2 O1 2 H2 O= Mn C2 O4 + 2 C O2 + 6 H2 O.

4

2

2

2

Similar experiments with mercuric oxide failed to give any satis factory result. The practical inference is that the compound known as sal acetos is by far the best agent for removing either iron-moulds or the disfiguring brown stains produced by Condy's fluids.

Means of Protecting Textile Fabrics, etc., from Fire. A. Paterno. (Ann. Chem. Pharm., clxi., 282-284; Journ. Chem. Soc., 2nd series, x., 337.) The author reviews several substances which are used for this purpose. Some of them, as sodium tungstate, answer very well, but are objectionable on account of the cost. The author has made numerous experiments with various substances in their power of rendering fabrics non-inflammable. He recommends the following as being quite equal to sodium tungstate. A mixture is made (shortly before required) of 4 parts of borax, and 3 parts magnesium sulphate; this is dissolved in 20-30 parts of warm water, and the dry fabric dipped into the solution, wrung out, and dried. The action seems to be to form an insoluble magnesium borate, which envelopes the fibres and prevents the escape of inflammable gases, thereby stopping the combustion. A second mixture consists of ammonium sulphate and gypsum. These mixtures may be used for such substances as crape, muslin, canvas, wood, and rope.

Preserving Paper Labels on Glasses. (Journ. Chem. Soc., 2nd series, X., 272.) The dry label is rubbed with a piece of paraffin, and smoothed with a glass rod.

Detection and Estimation of Paraffin in Stearin Candles. M. Hock. (Dingl. Polyt. Journ., cciii., 313-315; Journ. Chem. Soc., 2nd series, x., 526.) Makers of stearin candles mix paraffin with the fatty mass in quantities up to 20 per cent. Paraffin candle makers also mix stearic acid with their paraffin, and attribute valuable properties to such a mixture, as far as candle-making is

concerned. The attempt to determine if paraffin be present, and if so to get some approximate idea of the quantity, in a sample of stearin and vice versa, by means of the comparison of the melting point and specific gravity of such a mixture is shown to be useless, as these vary according to the source from which the paraffin is obtained, as also in the case of the stearic acid, since the pure commercial article is by no means a chemically pure article.

A good method for detecting the presence of stearic acid in paraffin has been devised by R. Wagner, viz., by treating a boiling solution of the paraffin in alcohol with an alcoholic solution of neutral lead acetate, when, if stearic acid be present, a dense floccular precipitate appears, but none if it be absent. The best method, and one which can be used quantitatively as well as qualitatively, is described as follows:-Not less than five drachms of candle are taken and treated with warm solution of potassium hydrate, which must not be too concentrated. A soap is formed with the stearic acid, whilst the paraffin is left unaltered. Sodium chloride is thrown into the solution, whereby the soap is separated out as soda soap, and in precipitating takes down the paraffin with it. The soap obtained is thrown on the filter and washed with cold water or very dilute spirits of wine. Thus, firstly, the sodium chloride is washed out, and finally the soap is brought into solution, and likewise washed through the filter, leaving the paraffin, which is then dried at a temperature below 35° C., so as not to fuse it. The paraffin is then treated on the filter with ether, and after repeated washing with this solvent, the ethereal solution is carefully evaporated in a weighed porcelain crucible, in the water-bath, at a low temperature. The residue, consisting of the paraffin, is then weighed, and the stearic acid is estimated by difference.

Colouring of Butter with Carrot-pigment. (Journ. Chem. Soc., 2nd series, ix., 968.) The colouring matter of carrots (carrotine), extracted by exhausting the dried and pulverised roots with bisulphide of carbon, is tasteless and scentless, and, consequently, better adapted to colouring butter than the generally used annatto.

The Manufacture of Yeast. (Journ. Pharm. Chim., 4th series, xiv., 273.) A kind of yeast is manufactured at Vienna which is said to possess greater activity than the ordinary kind. Three kinds of germinated grain are employed, maize, rye, and barley, and these are first macerated in water at 65° to 75° C., and after some hours the infusion is drawn off, and alcoholic fermentation started by the addition of a little yeast. A thick froth composed of yeast globules gradually collects upon the surface of the liquid,

and is removed, drained, and gradually submitted to strong pressure. It may then be kept from eight to fifteen days according to the season.

Coating of Metallic Articles with a nearly Costless, Permanent, Shining Black Coat. C. Puscher. (Dingl. Polyt. Journ., ceii., 92. Journ. Chem. Soc., 2nd series, x., 187.) The bodies to be coated are supported above the surface of some coal-dust strewn over the bottom of an iron box fitted with a lid, and the box is then set on a brisk fire. The vapours given off from the coal cover all the articles with an even black coat, which is not sticky, and has no smell even when hot.

Decoration of Metals. (Journ. Frankl. Inst., August, 1871.) Dr. Puscher recommends a solution composed of a mixture of 3 parts of hyposulphite of soda and 1 of acetate of lead, for the purpose of decorating metallic surfaces. When heated to about 100° C., this solution deposits a layer of sulphide of lead upon any metallic surface in contact with it; the effect of the peculiar colour of the metal beneath being to produce a great variety of tint.

The Colouring of Paper, Leather, etc., with Aniline Lakes. Ferd. Springmühl. (Dingl. Polyt. Journ., ccii., 382. Journ. Pharm. Soc., 2nd series, x., 339.) The author has accidentally discovered that every kind of paper, as also leather, linen cloth, etc., may be coloured to any extent by the use of an alcoholic solution of any aniline colour in a solution of resin. The same resin may be used for this purpose that is recommended by the author in colouring glass and mica, but an easily soluble lake must be employed, and for equal bulks of alcohol used in dissolving, much less of the resin containing lake must be used in this case.

The colour may be either applied to paper as a paint, or the paper may be soaked in the solution, and hung up to dry.

Ether Glue. (Scien. Amer.) An excellent liquid glue is made by dissolving glue in nitric ether. The ether will only dissolve a certain amount of glue, consequently, the solution cannot be made too thick. The glue thus made is about the consistency of molasses, and is doubly as tenacious as that made with hot water. If a few bits of indiarubber, cut into scraps the size of buckshot, be added, and the solution be allowed to stand a few days, being stirred frequently, it will be all the better, and will resist the dampness twice as well as glue made with water.

Waterproof Glue. (Dental Cosmos, August, 1871, Scien. Amer.) Ordinary glue can be rendered insoluble in water by adding to the water, with which it is mixed when required for use, a small

quantity of bichromate of potash, and exposing the articles to which it is applied to the light. Chromic acid has the property of rendering glue and gelatin insoluble. As the operation of heating the gluepot is usually conducted in the light, no special exposure of the articles to which it is attached need be made. It is probable that paper could be rendered impervious to water by pasting the sheets with this prepared glue. The bichromate is said to render rubber particularly hard and unattackable by hot water. The chromated gelatin ought also to be tried on parchment paper, wood, leather, and cloth fabrics. The proportion of bichromate to be taken must be ascertained by experiment; for most purposes one-fiftieth of the amount of glue will be found to suffice, that is, one pound of dry bichromate of potash to fifty pounds of dry glue.

Many applications of waterproof glue will readily suggest themselves to our readers. The Albert photographic process is founded upon this property of gelatin, and billiard-balls, buttons, and ornaments are now largely made of chromated glue.

A Vegetable Cement of great Adhesive Power. A. Selle. (Dingl. Polyt. Journ., cci., 182. Journ. Chem. Soc., 2nd series, ix., 971.) Two parts nitrate of lime, twenty-five water, and twenty parts powdered gum arabic, rubbed together in a mortar, form a transparent cement of remarkable strength, and applicable to wood, porcelain, glass, stone, etc. The surfaces to be united are painted with the cement, and bound together till drying is complete.

Litharge and Glycerin. (Phys. and Pharm., 1872, ii., 17.) M. Rost has made a material suited to a variety of purposes by mixing protoxide of lead (litharge) and glycerin so that they form a creamy liquid. In a short time the mixture becomes a hard and homogeneous mass, which readily adheres to metal, and resists the action of water and steam, and is not reduced by a temperature of 557° F. It is a valuable cement, and, in the fluid state, may be used in galvano-plastic copying.

A very desirable Cement for Iron. Dr. C. Winkler. (Pharmacist, v., 175.) Sixteen parts of powdered iron, three parts powdered muriate of ammonia, and two parts of flowers of sulphur, are mixed and kept on hand in a dry state, in which condition the mixture is unchangeable. When wanted, one part of it is mixed with twelve parts more of powdered iron, and so much water, acidified with a few drops of sulphuric acid, to form a stiff paste. This is applied to the parts to be cemented, which must be previously well cleaned and rubbed bright, then the piece is laid aside, and sufficient time allowed for the cement to dry.