Standard Solution of Ammonia ailorkle.—Dissolve P5735 grm. of dry ammenic chloride (the ordinary commercial kind is generally sufficiently pure for the purpose) in 1 litre of water. It is convenient to have a strong and weak solution as well. 100 c.c. of this solution is taken and made up to 1 litre ; 1 c.c. of this latter solution will contain •00015735 grm. of the salt, which corresponds to •00005 grm. of ammonia Distilled water, free from ammonia, and a solution of sodic carbonate, which must also be free from the slightest trace of ammonia, are also required for the application of the Nessler test.
Determination of Nitrogen as Ammunia.—Organic compounds containing nitrogen, which is con vertible into ammonia, are heated in a combustion tube with soda lime; the ammonia which is formed ie received in a suitable bulb apparatus containing a quantity of standardized hydrochloric acid. After complete condensation the excess is titrated with standard alkali. This method is used for the determination of nitrogen and ammonia in manurial substances. When it is desired to ascertain only the ammonia present, a small quantity of the substance—guano, for instanee—is boiled in a flask with caustic magnesia, and the liberated ammonia received in a condenser con taining standard acid as before. Soda or potash are not to be used in such eases, as they convert, in many instances, the nitrogenous constituents present into ammonia.
In the estimation of nitrogen by combustion with soda-lime, E. Mulder points out the following sources of error. The cork may absorb some ammonia, to prevent which the cork is recommended to be covered with tinfoil. If the hydrochloric acid is not sufficiently dilute, a small quantity of chloride is liable to be carried away with the hot steam. He recommends that the substance to be burned should firet be mixed with soda-lime in fine powder, and this mixture with a larger quantity of granulated soda-lime. An ammouiacal salt should be first mixed with carbonate of lime. For absorbing the ammonia he uses a U-tube, filled with fragments of glass moistened with hydro chloric acid. Dr. Knop has found that the column of soda-lime should not be too long, as the ammonia is likely, especially when strongly heated, to be decomposed.
An improved form of the Will and Varrentrapp apparatus has been recently devised by Mr. H. Shepherd, F.C.S., which has met with universal approval, for nitrogen determinations as ammonia. The bulb nearer the combustion tube, instead of being elongated into the ordinary form with a long bent tube, is supplied with a short neck, with a larger opening, so that the acid may be supplied more readily from a burette. This is gtted with an indiarubber cork, perforated. so as to admit a
short bent tube, for connecting with the combus tion apparatus. The ordinary forro of bulb, from the bent tube being fractured by the heat of the combustion furnace, rendered it necessary to use a fresh bulb apparatus for nearly every determina tion. Fig. 203 shows this bulb ; C is the combus tion tube, T the bent tube passing through, R an indiarubber cork, and B the absorption apparatus.
Mr. H. Shepherd, chemist to Messrs. 011endorff's Manure Works, Victoria Docks, recommends tincture of cochineal as indicator for these determinations, instead of litmus.
Small quantities of nitric acid, and nitrates or nitrites, are conveniently estimated by conversion into ammonia, which can be received in a condenser, when distilled, containing acid, or Nesslerized if the quantity be very small. Hydrate of soda and aluminium foil or filings (zinc answers as well), when dissolved in the presence of nitrates, give rise to the formation of ammonia, from the fact that nascent hydrogen decomposes the nitrie acid, and combining directly with the nitrogen thus set free. When a large quantity of zinc is rapidly dissolved, ammonia is formed from the direct combination of the nascent hydrogen with atmospherical nitrogen. It has been proposed to utilize this synthetical formation of ammonia by means of electrolytical hydrogen from water. The decompositions which occur in our atmosphere by heavy electrical disturbances show that ammonia and nitric acid are both formed.
Lithia. (FR., Lithine ; GER., Lithicm).—Formula Li02 ; combining weight, 39.
This substance, the oxide of the metal lithium, is an alkaline or earthy salt, and was discovered in the minerals petalite (silicate of aluminium and lithium) and triphane, in the year 1817, by Arfyedson. It is a white, caustic salt, possessing alkaline properties to an intense degree ; it has such a powerful affinity for water that it can only be obtained in the form of a hydrate. It has also the power of attacking or corroding platinum, so that, in its preparation, silver vessels should be employed in preference to those made of the former metal. Tbe hydrate has much the same taste, causticity and alkalinity as those of potash and soda, but it is not nearly so readily soluble in water. When held in the colourless flame of the Bunsen lamp, it imparts to it a rich crimson tinge, by which the presence of the metal lithium is recognized in qualitative analysis.