AMMONIA. —Estimation. 203

apparatus, c, by means of a caoutchouc connecter, a.The nitrogen apparatus has four bulbs, which arefilled with hydrochloric acid to the level represented;the apparatus rests upon a convenient support, D.By placing the long limb of the bulbed tube in asmall glass filled with the acid, and applying suctionto the other end, it is readily filled to the properheight. Great care must be taken that too muchacid is not admitted, as then there would be a risk ofspoiling the analysis by the liquid flowing back intothe combustion tube.

Before proceeding to the determination, the sub-stance should be thoroughly dried, either in thewater-bath or over sulphuric acid in the exhaustedreceiver of an air-pump; 10 to 20 grains are thentaken and mixed intimately with the soda lime in anagate or glass mortar, which should be placed upona large sheet of glazed paper, to prevent the loss ofany particles that may be accidentally dropped duringthe grinding and filling of the tube. As much of thesoda lime is put into the tube as is sufficient to fillabout J of an inch, and then the mixture of the sub-stance under examination and the lime compound isintroduced as speedily as possible. The mortar isrinsed with successive small quantities of the pow-dered soda lime, and these are added to fill up theempty part of the tube to within 2 inches of itsmouth. A loose plug of asbestos is now inserted,and the cork with small tube tightly fitted to it; aspace through which the products of the combustionmay traverse the tube is made by holding the latterin the hand, and giving it a few gentle taps horizon-tally against the table; the contents aggregate moreclosely, and an. empty space is formed in the upperpart. The tube is now placed in the furnace withthe pointed end upwards, as seen in the figure, andthe nitrogen apparatus attached by means of the con-necter. Care must be exercised that all the joiningsare air-tight; this the operator may ascertain byholding a glowing piece of charcoal to the inner bulb,till a few bubbles of expanded air escape to the middleone; • if, on removing the coal, the liquid assumesthe original level the connections are air-tight. Bed-hot pieces of charcoal are now applied to the pos-terior part of the tube for a short time, to expel theair contained in the apparatus; and after that thepieces are placed at the front end, and graduallyadded to as the contents become decomposed, till thewhole of the tube is at a low red heat. Particularpains should be taken to eliminate the ammoniagradually and steadily, and, above all, not to allowthe heat to fall at any part of the tube till all theammonia contained in that part is expelled; for onremoving the coals a vacuum is formed, which causesthe reflux of the hydrochloric acid from the nitrogenapparatus into the tube. Hence the coals should beapplied to a fresh part before the matter alreadydecomposing is completely exhausted.

When no more ammonia is given off, the pointedend of the tube is broken by a forceps, and suctionapplied to the long arm of the nitrogen apparatus,in order to draw over the last traces of ammonia thatmight remain in the apparatus; after which it is

detached, and the chloride of ammonium solutiontransferred to a beaker glass, or platinum dish, to-gether with the water used to rinse the bulbs, andthe whole evaporated to dryness.

The residue thus obtained is dissolved in as smalla quantity as possible of distilled water, filtered, andthe filtrate and washings precipitated by platinicchloride ; the solution is then evaporated, and treatedwith alcohol. The remainder of the operation isconducted in the same way as already described.The results, when the operation is carefully per-formed, are very accurate.

The soda-lime process may be shortened by takinga known weight of pure hydrochloric acid, the quan-tity of real acid in which may be ascertained eitherby specific gravity or by an aeidimetrical examina-tion. In this case, after the ammonia from the mix-ture in the combustion tube has been absorbed, thecontents of the nitrogen apparatus are transferred toa beaker glass together with the washings, and theexcess of acid neutralized with a standard solutionof ammonia.

Peligot determines this excess of acid by dissolv-ing caustic lime in a solution of sugar, and neutral-izing the acid with the solution thus obtained. Theliquid is preserved from contact with carbonic acidin well-stoppered bottles.

The saccharate of lime thus formed has an alkalinereaction, and neutralizes acids like an alkaline car-bonate. Its saturating power is tested with a dilutesolution of pure concentrated sulphuric acid.

Estimation by Brmnize.il Sodium Chloride .—A standardsolution of strongly alkaline sodium chloride contain-ing bromine sets free nitrogen when poured into asolution of ammonia. To prepare the solution:—Dissolve 1 part of sodium carbonate in 15 parts ofwater, cool the liquid with ice, and saturate it withchlorine whilst still cool, and add sufficient strongsolution of sodium hydrate to render the wholecaustic. Before using, add bromine in the propor-tion of 2 to 3 grains to the litre. (50 c.c. of thissolution will decompose fully 2 grains of ammoniumchloride). 'The solution is titrated with a solution ofsodium arsenite containing 4-95 grm. As.,0 3 in 1litre (1 c.c. = -0005GG grm. N1I 3 ) (see Chlorine).

Estimation by Nessla‘’s Solution (see Water).—When Nessler’s solution (a solution of mercuriciodide in potassium iodide and potassium hydrate)is added to a certain volume of fluid containing avery minute unknown quantity of ammonia, a certaintint is produced. And the unknown quantity ofammonia may be determined by imitating this tintwith a known quantity of ammonia.

The solutions used are:—1. A standard solutionof ammonia (1 c.c. = 1 mgrm. NII 3 ). This is pre-pared by dissolving -315 grm. of ammonium chloridein 1 litre of water. 2. Nessler’s solution.

Potassium iodide,. 3-5 grm.

Mercuric chloride,. 16 grm.

Water,. 40 c.c.

Potassium hydrate solution,. quant . svjf.

The potassium iodide is dissolved in 10 c.c. ofwater, the mercuric chloride in 30 c.c. of water. The