AMMONIA.— Distilling Apparatus. 185
hotter as it falls towards the under reservoir, whereit is retained for some hours at a boiling heat, toexpel all the alkali. On the contrary, when it isnecessary that the ammoniacal vapour should be incompany with much steam, the stream of liquidentering is elevated to nearly its boiling point in thetop diaphragms, by means of the larger volume ofsteam which is admitted from the boiler. Concen-trated or dilute solutions of ammonia may in thisway be obtained at once from salts, the acids ofwhich are removed in the usual manner by lime oralkali; a product of considerable purity is alsoderived from the ammoniacal liquids formed by thedistillation of bones or other animal matters; butbefore submitting such liquids to the action of theheat, it is necessary to remove most of the impuritiesand the combined acid by the action of lime.
It is customary to have the diaphragms bent up-wards, alternately, at opposite sides, so as to conductthe liquid from right to left, and conversely, till itreaches the bottom.
Carbonic acid gas, and other volatile compoundswhich do not impair the use of ammonia in certainapplications, may in using this still be given off withthe ammonia; but in this case as much steam shouldbe generated as will prevent the absorption of theammonia gas by the carbonic acid.
Laming recommends that the solution of ammo-nium carbonate, as obtained from bones, should bedecomposed by means of chloride of calcium, insteadof the mineral acids which are usually employed forthat purpose; carbonate of lime is formed, and chlorideof ammonium remains in solution. After filteringor siphoning this liquid, he boils it for an hour, bywhich treatment any gaseous impurities are expelled.As soon as the liquid has cooled, it is agitated, firstwith sufficient hydrated oxide of iron to precipitateany hydrogen sulphide (II 2 S) that may still remain,and next with enough lime to saturate the wholeof the combined hydrochloric acid; it is then dis-tilled. By this treatment a tolerably pure solutionis produced.
It is to be observed, that when ammonia is preparedon the large scale according to the method firstdescribed, the dry salt and lime are often mixed in theretort, and as operations are about to commence, aquantity of water is added for the purpose of slakingthe lime, and preventing the mass adhering to thebottom of the retort; by this means so much heat isgenerated that a considerable quantity of the ammoniais driven over to the receivers, and thus fuel iseconomized. To prevent the residue hardeningwhen the distillation is carried to dryness, it iscustomary to add a few spadefuls of common saltto the mass.
An ingenious apparatus, which may be taken astypical of that now commonly employed for extrac-tion of ammonia from gas liquor, &c., was recentlydevised and patented by Ei/wert and P ack. Theform of apparatus will be readily understood by thefollowing description referring to the accompanyingdrawings. (Figs. 5, 6, and 7). The same lettersrefer to the same parts in each figure.
VOL. i.
A vessel capable of holding the charge of ammo-niacal liquor is so fixed that it may receive the liquorsfrom the tank or reservoir of crude ammoniacalliquor. In this vessel the gas liquor is mixed withthe proper quantity of lime, and then run into aboiler.
On the application of the fire to the boiler theammoniacal vapour as it escapes is led by a pipeback into the first vessel, and allowed to escape intothe liquid at its lowest portion; as the gas rises itabsorbs fresh portions of ammonia, and thus en-riched by the ammoniacal liquor, is led into a con-densing chamber, the more condensible portionrunning back into the first vessel. The more vola-tile vapour is carried through a refrigerating wormto a condensing tank where the hydrocarbons,some free ammonia, and sal-ammoniac is retained.The purer and uncondensed vapour passing onis conducted into vertical purifiers filled withcharcoal, and thence into the stock condensingchamber.
On the dome or upper part of the wrought-ironboiler a is adapted the tube a, a, which passingupwards for a certain distance is then turned down-wards, and enters through a tight joint into the vesselAj nearly to the bottom; it is then carried along nearlythe whole length of A r and is pierced with numerousholes for the escape of the gas passing from the boilerA into this pipe or tube a, a.
On the dome of the vessel Aj is adapted the tubeb, b, turned down as a siphon, the other branchgoing to within 12 inches of the bottom of thevessel B, which is in communication with A x by thetube 1.
On the cover of the vase B is fixed the tube c,which leads the aqueous ammoniacal vapours intothe coil of the refrigerator c. The tube c, when itleaves the refrigerator, is carried to within 8 inches ofthe bottom of the vessel D, fitted with a safety tubed, and a cock opening a communication by the tubep between the vessel D and the boiler A r
In the vessel D are deposited the aqueous ammo-niacal vapours condensed by the worm, whilst theammoniacal vapour passes by the tube e to traversefour cast-iron tubes, e, Ej, e 2 , e s , communicat-ing by the tubes these four tubes, open at
each end, are fitted with rims so that each end maybe closed with a tight fitting cast-iron cover.
From the tube E s the ammoniacal vapours arecarried by the leaden tube g into a lead condensingcistern G, fitted with a funnel-shaped safety tube hand a cock for emptying at t ; the bent tube i takesthe non-condensed gas in G into the vessel H, whichis also fitted with a tap for emptying a funnel-shapedsafety tube j, and a tube k for the last uncondensibleportions of the gas; the latter should be led awayfrom the factory.
The crude ammoniacal liquors are introduced bythe tube and cock q , which is in communication witha reservoir above the level of the tank A r The capa-city of the boiler Aj is about 300 gallons. The milkof lime is thrown in hot through the hole r.
The emptying of the vessel a x into the boiler a is
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