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In a paper lately presented to the Academie des Sciences, Messrs. Besson and Troost bring out the action of peroxide of nitrogen upon ammonia and its salts. Before attempting to use peroxide of nitrogen as a solvent for the ammoniacal salts, they observed the following points. If we bring ammonia gas which is liquefied and solidified at --80 in contact with solid peroxide of nitrogen cooled to the same degree, a violent explosion is produced, giving off abundant fumes. The reaction is more moderate if we bring a current of dry ammonia gas cooled to --20 degrees upon the cooled peroxide of nitrogen contained in a tubulated retort, the latter being connected with a condenser. A vacuum has first been made in the apparatus. The reaction causes a great heat, and a temporary formation of nitrous acid as a green liquid, also giving off white fumes. The gases given here are formed essentially of nitrogen mixed with nitric oxide, N O. When the reaction stops there remains in the crucible a white salt which consists of nitrate of ammonia. The main reaction of the ammonia gas upon the peroxide of nitrogen in the above case is as follows: (a) 3 N 02 4 N H3 7 N 6 H2 O. (b) 3 N O2 2 N Hs HL> 0 NO-2 (N 03 N H4). The peroxide of nitrogen acts slowly when cold upon N H4 CI, which is liquefied at its contact. To complete the reaction it is well to heat for some time to 100 deg. C. in sealed and strong tubes. The considerable gas pressure which we observe on opening the tubes is due to chlorine and a mixture of nitrogen and nitrous oxide. As to the brownish liquid remaining in the tubes, it is separated by fractional distillation into oxy-chloride compounds of nitrogen, nitrous anhydride, an excess of nitrogen peroxide, nitric acid and a residue consisting of a little nitrate of ammonia. It is found that peroxide of nitrogen acts upon nitrate and -sulphate of ammonium in the same way as upon the ' chloride, but only nitrogen is given off in this case. The liquefied mass forms two superposed layers. The upper layer is formed of peroxide in excess. 'After eliminating it by distillation, there remains nitric acid in the first case, and a mixture of nitric and sulphuric acids in the second. Messrs. Bordas and Touplain, of Paris, have lately brought out a new method of determining the different foreign products contained in cocoas and chocolates. In the observations which they made on high-speed centrifugal separators for the rapid analysis of alimentary matters such as milk, chocolates, cocoas, etc., they found that the elements in suspension in the liquid are deposited in the tubes of the apparatus in the order of their density. This was especially evident for the insoluble matters composing the chocolates and cocoas. In the insoluble part of the deposit they could distinguish well-defined series, having different colors. They wished to utilize this so as to separate not only the different elements which compose the chocolates, but also the waste products which they may contain, such as hulls, etc., as well as matter which is purposely added for adulteration. Up to the present it was found to be a difficult. matter to separate the waste parts of the plant and it was almost impossible to detect small quantities of foreign bodies. Microscopic examination was a long and often unfruitful operation and we cannot estimate even approximately the amount of foreign matter contained in the chocolate or cocoa. The authors found a method which is practical and gives good results in separating the foreign bodies. The process consists in preparing a series of liquids of variable densities from 1,340 to 1,600 in which the powders mixed with the liquids will either sink to the bottom or float on the surface. Tetrachloride of carbon is used to start with, and by diluting it with benzine we diminish the density as desired and obtain a series of liquids having known densities. Naturally, we must first free the chocolate from its fatty matter as well as from bodies which are soluble in water, and the insoluble part is pulverized and dried. The precipitation of the powder is facilitated by using the centrifugal apparatus, and by a series of simple de- cantations we can separate the floating parts from the portions which are precipitated to the bottom of the tube. ' The product is collected on a filter and it is weighed after a previous microscopic examination. By this very simple method we may thus examine ehoco- late and cocoa, besides other food products reduced to powder, such as coffee, pepper and spices
