and ashes, and these impurities fell to the bottom of the water bath. The gases after this process are divested of the greater part of any tarry impurities which they may have possessed, and are ready for the final purification, in which ammonia is extracted. This is effected by means of a series of shallow trays, covered with water or weak acid, and pierced with a number of fine holes, through which the gas is made to bubble. The washing apparatus is therefore strangely similar in principle to that designed by Mr G. Livesey. M. Chevalet states that this double process is applicable to gas works as well as to the purification of smoke, with the difference that for the latter purpose the washing trays are filled with acid for the retention of ammonia, while in the former application gas liquor or water is used. The arrangement is said to be a practical success.--_Journal of Gas Lighting._ * * * * * DETERMINATION OF NITROGEN IN HAIR, WOOL, DRIED BLOOD, FLESH MEAL, AND LEATHER SCRAPS. BY DR. C. KRAUCH. Differences obtained in the estimation of nitrogen in the above substances are frequently the source of much annoyance. The cause of these discrepancies is chiefly due to the lack of uniformity in the material, and from its not being in a sufficiently fine state during the combustion. The hair which is found in commerce for the manufacture of fertilizers, is generally mixed with sand and dust. Wool dust often contains old buttons, pieces of wood, shoe pegs, and all sorts of things. The flesh fertilizers are composed of light particles of flesh mixed with the heavier bone dust. Even after taking all possible precautions to finely comminute these substances by mechanical means, still only imperfect results are obtained, for the impurities, that is to say, the sand, can never be so intimately mixed with the lighter particles that a sample of 0.5 to 0.8 gramme, such as is used in the determination of nitrogen, will correspond to the correct average contents. In substances such as dried blood, pulverization is very tedious. A very good method of overcoming these difficulties, and of obtaining from the most mixed substances a perfectly homogeneous mass, is that recommended by Grandeau[1] of decomposing with sulphuric acid--a method which as yet does not seem to be generally known. From a large quantity of the substance to be examined, the coarse stones, etc., are removed by picking or sifting, and the prepared substance, or in cases where the impurities cannot be separated, the original substance, is treated with sulphuric acid; after it is decomposed, the acid is neutralized with calcium carbonate, and the nitrogen is determined in this mass. [Footnote 1: _Handbook d. Agrict. Chem. Analyst._, p. 18.]