870 



HYDROCHLORIC ACID 



of the specific gravity by 200. Thus, for example, at 1-162 we shall have by this rule, 

 0-162 x 200 = 32-4, for the quantity of gas in 100 parts of the liquid. 



The preparation of this acid upon a commercial scale is frequently effected in this 

 country by acting upon common salt in hemispherical iron pots, or in cast-iron 

 cylinders, with concentrated sulphuric acid ; taking 6 parts of the salt to 5 of the acid. 

 The mouth of the pet may be covered with a slab of siliceous freestone, perforated 

 with two holes of about two inches in diameter each, into the one of which the acid is 

 poured by a funnel in successive portions, and into the other, a bent glass, or stone- 

 ware tube, is fixed, for conducting the disengaged muriatic gas into a series of large 

 globes of bottle glass, one-third filled with water, and laid on a sloping sand-bed. A 

 week is commonly employed for working off each pot ; no heat being applied to it till 

 the second day. 



The decomposition of sea-salt by sulphuric acid was at one time carried on by 

 some French manufacturers in largo leaden pans, 10 feet long, 5 feet broad, and a foot 

 deep, covered with sheets of lead, and luted. The disengaged acid gas was made to 

 circulate in a conduit of glazed bricks, nearly 650 yards long, where it was condensed 

 by a sheet of water exceedingly thin, which flowed slowly in the opposite direction of 

 the gas down a slope of 1 in 200. At the end of this canal nearest the apparatus, the 

 muriatic acid was as strong as possible, and pretty pure ; but towards the other end, 

 the water was hardly acidulous. The condensing part of this apparatus was therefore 

 tolerably complete ; but as the decomposition of the salt could not be finished in the 

 leaden pans, the acid mixture had to be drawn out of them, in order to be completely 

 decomposed in a reverberatory furnace ; in this way nearly 50 per cent, of the 

 muriatic acid was lost. And besides, the great quantity of gas given off during the 

 emptying of the lead-chambers was apt to suffocate the workmen, or seriously injured 

 their lungs, causing severe haemoptysis. 



The apparatus for condensing muriatic acid gas has been modified and changed, of 

 late years, in many different ways. 



The Bastringue Apparatus. At the end of a reverberatory furnace, a rectangular 

 lead trough or pan, about 1 foot deep, of a width equal to that of the interior of the 

 furnace, that is, about 5 feet wide and 6 feet long, is encased in masonry, having its 

 upper edges covered with cast-iron plates or fire tiles, and placed upon a level with 

 the passage of the flame, as it escapes from the reverberatory. The arch which covers 



1203 



that pan forms a continuation of the roof of the reverberatory, and is of the same 

 height. The flame which proceeds from the furnace containing the mixture of salt 

 and sulphuric acid is made to escape between the vault and the surface of the ii-on 

 plates or fire tiles, through a passage only 4 inches in height. When the burned air 

 and vapours reach the extremity of the pan, they are reflected downwards, .m<l 

 made to return beneath the bottom of the pan, in a flue, which is afterwards divided 

 so as to lead the smoke into two lateral flues, which terminate in the chimney. Tim 

 pan is thus surrounded as it were with the heat and flame discharged from the 

 reverberatory furnace. A door is opened near the end of the pan, for introducing 

 the charge of sea-salt, amounting to 12 bags of 2 cwts. each, or 24 cwts. This door is 

 then luted on as tightly as possible, and for every 100 parts of salt, 110 of sulphuric 

 acid are poured in, of specific <rr;ivity 1 -.V.)4, containing 57 per cent, of dry acid. 

 This acid is introduced through a funnel inserted in the roof of the furnace. l)r..in- 

 position ensues, muriatic acid gas mingled with steam is disengaged, and is conducted 



