94 



CHEMISTRY. 



pose, and the bromide of silver, likewise spe- 

 cially prepared, for comparison. The mean of 

 a series of eight experiments gave 1 1 _':> 1 as the 

 atomic weight of the metal. This determina- 

 tion is regarded as bearing against the validity 

 of the hypothesis of Prout, that all atomic 

 weights are multiples of that of hydrogen. 



NEW PBOOBSSKS. Mr. Alfred H. Allen has in- 

 dicated some valuable simple tests for the pres- 

 ence of hydrocarbon oils as adulterations in 

 animal and vegetable oils. The methods for 

 the detection of these oils are based on the 

 density of the sample, the lower flashing and 

 boiling points, the fluorescent character of the 

 oils produced from petroleum, bituminous 

 shale, and rosin, and the incomplete saponifi- 

 cation of the oil by alkalies. The taste of the 

 oil and its odor on being heated are also use- 

 ful indications. If undoubtedly fluorescent, an 

 oil certainly contains a mixture of some hydro- 

 carbon, but the converse is not strictly true, as 

 the fluorescence of some varieties of mineral 

 oil can be destroyed by chemical treatment, 

 and in other cases fluorescence is wanting. 

 The greater number of hydrocarbon oils em- 

 ployed for lubricating purposes are, however, 

 strongly fluorescent, and the remainder usually 

 become so on treatment with an equal measure 

 of strong sulphuric acid. If strongly marked, 

 the fluorescence of a hydrocarbon oil may be 

 observed in presence of a very large proportion 

 of fixed oil, but, if any doubt exist, the hydro- 

 carbon oil may be isolated. The fluorescence 

 may be seen by holding a test-tube filled with 

 the oil in a vertical position in front of a win- 

 dow, when a bluish " bloom " will be perceived 

 on looking at the sides of the tube from above. 

 A glass rod dipped in the oil and laid on a 

 table in front of the window so that the oily end 

 shall be projected in the view against the dark 

 background of the floor, or a piece of black 

 marble or smoked glass rubbed with a streak 

 of oil and held horizontally before a window, 

 will make a very slight fluorescence, readily 

 perceptible. Turbid oil should be filtered, to 

 get out the minute particles that might, by 

 reflection, give an appearance of fluorescence. 

 Dilution with ether, to which a little mineral 

 oil imparts a strong blue fluorescence, gives an 

 excellent test. The hydrocarbon oil may be 

 driven off by heating it if its boiling-point is 

 comparatively low, but may be better removed 

 and the quantity of it measured by saponifying 

 it, and washing the solution of the soap with 

 ether. The hydrocarbon may, in this case, be 

 recovered pure by separating the ethereal layer 

 and evaporating it at or below a steam-heat. 

 A good alkaline preparation for this purpose 

 can be made by dissolving caustic potash in 

 methylated spirit. The washing with ether 

 should be repeated several times. The ether- 

 process is, however, not applicable to sperma- 

 ceti and the waxes, on account of the large 

 quantities so small in the other fats that it 

 need not be taken into account of matter they 

 contain that is not acted upon by the alkalies 



but is dissolved by ether. The nature of the 

 hydrocarbon oil may be determined after it 

 has been isolated, by observing its density, 

 taste, smell, behavior with acids, and other 

 qualities. 



Professor G. Lunge, of Zurich, has perfected 

 and described a simple and inexpensive process 

 for procuring pure naphthalen that will not 

 discolor. Presuming that the discoloration of 

 naphthalen is analogous to that of phenol, he 

 sought to remove the agent which caused it by 

 oxidation. For this purpose he added an oxi- 

 dizing agent in the ordinary chemical washing 

 of naphthalen, using manganese dioxide, with 

 complete success. Other oxidizing agents might 

 be substituted for manganese dioxide, but a 

 cheaper one can hardly be obtained. Naphtha- 

 len prepared by this process has kept its pure 

 white color much longer than the " chemically 

 pure " naphthalen made by the secret process 

 of the manufacturers. 



A patent has been taken out by M. Closson, 

 of Paris, for a cheap and expeditious method 

 of obtaining magnesia from magnesium chlo- 

 ride. The crude lye of magnesium chloride is 

 treated with burned dolomite, or magnesian 

 limestone, when the chlorine of the lye com- 

 bines with the lime of the dolomite, so that if 

 the latter is pure a magnesia of from 98 to 99 

 per cent standard can be easily made on a large 

 scale. The magnesia bricks prepared by this 

 process at Leopoldshall resist even the flame of 

 the oxyhydrogen-blast. The cost is fifteen 

 shillings a ton. Sulphate of lime is obtained 

 as a by-product of the process through the use 

 of calcium chloride to remove the magnesium 

 sulphate that is present in the magnesium chlo- 

 ride, and is used by paper-makers under the 

 name of pearl-hardening. The value of the 

 new process in its bearing on the manufacture 

 of fire-proof furnace-linings, crucibles, etc., is 

 very great. 



Herr A. Wagner recommends the following 

 process, which has proved very satisfactory 

 for the limestone waters of Munich, for the 

 determination of the organic matter in water. 

 After the determination of all the other con- 

 stituents of the water, he evaporates suitable 

 quantities to dryness and separates the dry 

 residue by means of distilled water into an 

 insoluble and a soluble portion, the latter of 

 which contains the chief bulk of the organic 

 bodies. In the insoluble portion, which in the 

 waters he has to deal with consists almost en- 

 tirely of calcium and magnesium carbonates, 

 he determines the organic matter by igniting 

 a dried specimen in a platinum crucible and 

 treating subsequently with ammonium carbon- 

 ate in the customary manner. The portion 

 soluble in water, if nitrates are absent or are 

 present only in a quantity too small to be de- 

 termined, is dried after evaporation in a plat- 

 inum capsule, weighed, heated to a very low 

 redness, and weighed again. If nitrates are 

 present in larger quantities, so that the exist- 

 ing organic matter would not suffice to con- 



