&c. The scum is separated, and the fat becomes clear and transparent. When it is cooled it is washed by malaxation many times with water, till the salt is removed. It is then held in a state of fusion, at a temperature sufficient to evaporate all the water, without injuring the fat.-Bulletin de la Société de Pharm. de Bruxelles. ANILIN BLACK USED AS INDELIBLE INK FOR LINEN. BY DR. JACOBSEN. This ink should be kept in the form of the two following solutions: I. Solution of Copper. Take 8.52 gms. crystallized chloride of copper, 10.65 gms. chlorate of soda, 5.35 chloride of ammonium, and dissolve these in 60 gms. of distilled water. II. Solution of Anilin. Dissolve 20 gms. chlorohydrate of anilin in 30 gms. of distilled water, and add to it 20 gms. of a solution of gum arabic (1 gum to 2 of water) and 10 gms. of glycerin. On mixing four parts of the anilin solution with one part of the copper solution, a greenish liquid is obtained, which can be used immediately to write on the linen, but it changes after several days. It is necessary, therefore, to keep the solutions. separate until wanted. The characters may be traced with a pen, brush or pencil; if the liquid does not flow well in the pen it may be diluted sufficiently without fear of diminishing the intensity of the color, which appears first pale green, and becomes gradually black by exposure to the air. The writing may be rendered black instantly by passing over it a hot iron, or heating moderately the under side over a spirit lamp. It is even better to expose it to a current of steam, which is sufficient to develope instantly the anilin black. After this treatment the tissue is washed with warm soapsuds, when the characters will present a· beautiful blue black hue. This ink resists acids and alkalies," and if the ink has penetrated the linen so as to render the characters visible on the reverse, there is no fear that the color will be altered by lye.-Jour. de Chim. Méd., June, 1868. ON ROSANILIN AS A REAGENT FOR FREE FATTY ACIDS, AND FOR COD-LIVER OIL. BY DR. F. JACOBSEN. The author finds that rosanilin is insoluble in neutral fatty oils, but is at once colored pale red, more or less deep, if the oil is rancid, or has any free oily acid present, and if very rancid, as deep as gooseberry juice. The fuchsin of commerce (muriate, arseniate, &c., of rosanilin) dissolves in neither neutral or rancid oils, or fat acids. Oleic acid and all the fatty acids dissolve rosanilin immediately in great quantity, and are deeply colored. The oleate of rosanilin dissolves in all proportions in the oils and neutral fats. The rosanilin, for this reason, can be employed to detect free acid in mixtures of oils. The author proposes this reagent as a means of detecting the so-called bleached cod-liver oil sold in the European markets, which is not cod-liver oil, but the oily fats of different marine mammals, or those oils prepared by shaking with potash lye, and allowed to stand till clarified. As the medical properties of cod-liver oil should be partly attributed to the free fat acids that it contains, the white oil thus prepared possesses properties analogous to the neutral fish oils, and, unless rancid, are not colored by anilin. In some lubricating oils oleic acid residues have been used as an adulteration, which this test will easily discover. When an oil contains but very little free acid, the test should be applied as a saturated solution of rosanilin in absolute alcohol, a few drops added to the oil, and heated in a water-bath with stirring until the alcohol is evaporated. If no free fatty acid is present no coloration is produced, and the test separates, and is deposited at the bottom of the vessel, or remains in suspension as a brownish powder. Specimens of Provence oil and oil of sweet almonds did not color; oil of poppy seed slightly red; linseed oil deeply red, modified by the yellow color of the oil; castor oil colors yet more decidedly. Olive oil, mixed with five per cent. of oleic acid, is tinted like gooseberry juice.-Jour. de Chim. Med., from Neues Jahr. für Pharm. ON HYDRARGYRI IODIDUM VIRIDE, B. P. By C. H. WOOD, F.C.S, The "Green Iodide of Mercury" of the British Pharmacopoeia is clearly intended to be identical with the "Iodide of Mercury" of the London Pharmacopoeia. This is expressly implied by the "Synonym HYDRARGYRI IODIDUM Lond." given in the description of the preparation in the last edition of the British Pharmacopoeia. In both works the chemical compound mercurous iodide is obviously meant, and the British Pharmacopæia defines this by giving the formulæ "Hg,I or HgI." But the London Pharmacopoeia, in describing this compound, states, that "when freshly prepared it is dingy yellow;" while the British Pharmacopoeia names it "Green Iodide," and describes it as "a dull green powder." This discrepancy occurring in the description of a definite chemical body is a little remarkable, and requires some explanation. The processes and the proportions of ingredients given in the two Pharmacopoeias are almost identical; yet according to one authority we obtain a yellow, and according to the other a green product. I have frequently made the iodide of mercury according to the London Pharmacopoeia, and have always found that it possessed a dull yellow color, certainly with a shade of green upon it, but nevertheless the yellow vastly preponderating. Yet chemical authorities generally indicate that mercurous iodide is a green substance. In Gmelin's Chemistry' mercurous iodide is variously described as "a green," "a dark green," and "a yellowish-green;" but no mention is made of its being yellow. The British Pharmacopoeias of 1864 and 1867 are therefore in accord with the leading chemical manual. Being desirous of understanding this matter more perfectly, I made a few experiments to elucidate the point. Upon repeating the process as given in the British Pharmacopoeia, I found that the first effect of triturating the mercury and iodine with the spirit was to obtain a red color; due, no doubt, firstly to the solution of the iodine, and secondly to the formation of the red iodide of mercury; but after continuing the trituration for some time the mass became a decided dark green. This then was the point at which I was to transfer the product to filteringpaper and dry it by exposure in a dark room. But instead of doing this I continued the trituration until the mass was dry. As the rubbing proceeded I found the green color rapidly disappeared, the powder became more and more yellow, and the ultimate result was a yellow substance with a dingy greenish tint upon it. The question that arose, therefore, was to ascertain the composition of the product at the two periods; namely, at the period in which it was decidedly green, and at the subsequent period when it became permanently yellow. To solve this point 200 grains of mercury and 127 grains of iodine were triturated with a little spirit until the dark green color was obtained. A portion of this iodide was then taken for immediate analysis, and the remainder put in a dark place to dry. The analysis was effected as follows :— A known quantity of the iodide was washed with boiling absolute alcohol, the washings evaporated to dryness, and the residue weighed; it consisted of red or mercuric iodide. The insoluble portion was dried and divided into two parts; one was dissolved in hydrochloric acid and chlorate of potash, the solution evaporated to near dryness, diluted, precipitated with stannous chloride, and the precipitated metallic mercury collected and weighed; the other half of the powder was digested with finely granulated zinc and diluted acetic acid, whereby an amalgam of zinc was formed, the iodine passing into solution as hydriodic acid. After some time the liquid was poured off, nitrate of silver added to it, and the precipitated iodide of silver collected and weighed. Other methods of analysis were also employed, but the above were found sufficiently satisfactory. As some objections might be taken to the use of boiling alcohol, the red iodide was also estimated by washing with ether. The result of the analysis of the green powder was as follows, the moisture being excluded : : Mercuric Iodide, HgI, 28.6 58.4 13.0 100.0 It thus became evident that the green product was far from what it should be, according to the formula given by the Pharmacopœia. I then prepared some of the iodide, continuing the trituration until the green color had passed to the dingy yellow, which, according to the London Pharmacopoeia is characteristic of the product. A portion of this compound was then analysed, and the following results obtained : On comparing these numbers with those preceding it will be seen that by continuing the trituration the red iodide had to a great extent disappeared, and so had the free mercury. No doubt these two substances had entered into combination and formed a further portion of the mercurous iodide. The results so far, then, seem to admit of an easy explanation. By the constant trituration the last portions of the metallic mercury reach a state of extremely fine divisions. In this state the metal possesses somewhat of a blue color (well known to us in blue pill, etc.,) which, mixed with the yellow of the mercurous iodide already formed, would produce a green. According to this view, therefore, the green of the iodide is due to a mechanical mixture of mercurous iodide and mercury. It equally follows from this that the true color of pure mercurous iodide must be yellow. This explanation derives additional support from the fact that the green powder cannot be obtained and kept of any uniform tint. As first got it is a decided grass-green, but even while it is drying, however carefully the light be excluded, the color changes, approaching more and more to yellow. At the same time that this change goes on the proportion of mercuric iodide diminishes, and consequently the proportion of metallic mercury must diminish also, thereby lessening the green and augmenting the yellow color. In Gmelin's Handbook' three iodides of mercury are described; namely, the mercurous iodide, the mercuroso-mercuric |