AMMONIUM, CHLORIDE OF 



151 



round cistern receives the drainings of the mother-waters. The pump is made of 

 lead hardened with antimony and tin. 



The subliming furnace is shown infys. 43 and 44, by a transverse and longitudinal 

 section ; a is the ashpit ; b, the grate and fireplace ; c, the arch above them. This 

 arch, destined to protect the bottles from the direct action of the fire, is perforated 

 with vent-holes, to give a passage to the products of combustion between the sublim- 

 ing vessels ; d, d, are bars of iron, upon which the bottom of the bottles rests ; c, 

 stoneware bottles, protected by a coating of loam from the flame. 



45 



46 



Fig. 45 shows the cast-iron plates, a, b, c, which, placed above the vaults, receive 

 each two bottles in a double circular opening. 



At the extremity of the above furnace, a second one, called the drier, receives 

 the products of the combustion of the first at A, under horizontal cast-iron plates, 

 and upon which the bottom of a rather shallow boiler, is, rests. After passing 

 twice under these plates, round a longitudinal brick partition, b, b', b", the products of 

 combustion enter the smoke chimney, c. See plan, fig. 46. 



The boiler set over this furnace should have no soldered joints. It may be 3 feet 

 broad, 9 or 10 feet long, and 1 foot deep. The concrete sal-ammoniac may be 

 crushed under a pair of edge millstones, when it is to be sold in powder. 



Bones, blood, flesh, horns, hoofs, woollen rags, silk, hair, scrapings of hides and 

 leather, &c., may be distilled for procuring ammonia. When bones are used, the 

 residuum in the retort is bone-black. The charcoal from the other substances will 

 servo for the manufacture of Prussian blue. The bones should undergo a degree of 

 calcination beyond what the ammoniacal process requires, in order to convert them 

 into the best bone-black ; but the other animal matters should not be calcined up to 

 that point, otherwise they are of little use in the Prussian blue works. If the bones 

 bo calcined, however, so highly as to become glazed, their decolorising power on 

 syrups is nearly destroyed. The other substances should not be charred beyond a 

 rod-brown heat. 



The condensed vapours from the cylinder-retorts afford a compound liquor holding 

 carbonate of ammonia in solution, mixed with a large quantity of empyreumatic oil, 

 which floats at top. Lest incrustations of salt should at any time tend to obstruct the 

 tubes, a pipe should bo inserted within them, and connected with a steam-boiler, so as 

 to blow steam through them occasionally. 



The whole liquors mixed have usually a density of 8 or 9 Baume (1'060). The 

 simplest process for converting their carbonate of ammonia into the chloride of am- 

 monium is to saturate them with hydrochloric acid, to evaporate the solution in a 

 leaden boiler till a pellicle appears, to run it off into crystallisers, and to drain the 

 crystals. Another process is, to decompose the carbonate of ammonia, by passing its 

 crude liquor through a layer of sulphate of lime, 3 or 4 inches thick, spread upon 

 the filters, fig. 42. The liquor may be laid on with a pump ; it should never stand 

 higher than 1 or 2 inches above the surface of the bruised gypsum, and it should bo 

 closely covered with boards, to prevent the dissipation of the volatile alkali in the air. 

 When the liquor has passed throiigh the first filter, it must bo pumped up on to the 

 second ; or the filters being placed in a terrace-form, the liquor from the first may 

 flow down upon the second, and thus in succession. The last filter should bo formed 

 of nearly fresh gypsum, so as to insure the thorough conversion of the carbonate into 

 sulphate. The resulting layers of carbonate of lime should be washed with a little 

 water, to extract the sulphate of ammonia interposed among its particles. Tho am- 

 moniacal liquor thus obtained must be completely saturated, by adding the requisite 

 quantity of sulphuric acid ; even a slight excess of acid can do no harm. It is then 

 to bo evaporated, and the oil must bo skimmed off in the course of the concentration. 



