HYDROCHLORIC ACID 



871 



through 4 stone-ware tubes into the refrigerators, where it is finally condensed. These 

 refrigerators consist of large stone-ware carboys, called dame-jeannes in France, to the 

 number of 7 or 8 for each pipe, and arranged so that the neck of the one communi- 

 cates with the body of the other ; thus the gas must traverse the whole series, and gets 

 in a good measure condensed by the water in them, before reaching the last. 



When the operation is finished, the door opposite the pan is opened, and the 

 residuum in it is discharged, in the form of a fluid magma, upon a square bed of 

 bricks, exterior to the furnace. This paste speedily concretes on cooling, and is then 

 broken into fragments and carried to the soda manufactory. The immense quantity 

 of gas exhaled in discharging the pan, renders this part of the operation very painful 

 to the workmen, and wasteful in reference to the production of muriatic acid. The 

 difficulty of luting securely the cast-iron plates or fire tiles which cover the pan, the 

 impossibility of completing the decomposition of the salt, since the residuum must be 

 run off in a liquid state, finally, the damage sustained by the melting and corrosion of 

 the lead, &c., are among the causes why no more than 80 or 90 parts of muriatic acid 

 at 1-170 are collected, equivalent to 25 per cent, of real acid for every 100 of salt em- 

 ployed, instead of much more than double that quantity, which it may be made to 

 yield by a well-conducted chemical process. 



The cylinder apparatus is now much esteemed by many manufacturers. Fig. 1203 

 represents, in transverse section, a bench of iron cylinder retorts, as built up in a 

 proper' furnace for producing 

 muriatic acid; and fig. 1204 

 a longitudinal section of one 

 retort with one of its car- 

 boys of condensation, a is 

 the grate ; b, a fireplace, in 

 which two iron cylinders, 

 c c, are set alongside of each 

 other. They are 5 5 feet 

 long, 20 inches in diameter, 

 about of an inch thick, and 

 take 1:6 cwt. of salt for a 

 charge ; d is the ashpit ; e e 

 are cast-iron lids for closing 

 both ends of the cylinders; 

 /is a tube in the posterior 

 lid, for pouring in the sul- 

 phuric acid ; g is another 

 tube, in the anterior lid, for the insertion of the bent pipe of hard glazed stone- ware 

 h Us a. three-necked stone-ware carboy ; k is a safety-tube ; I, a tube of communi- 

 cation with the second carboy ; mmmm are the flues leading to the chimney n. 



After the salt has been introduced, and the fire kindled, 885- per cent, of its weight 

 of sulphuric acid, of sp. gr. 1-80, should be slowly poured into the cylinder through 

 a lead funnel, with a siphon-formed pipe. The three-necked carboys may be either 

 placed in a series for each retort, like a range of Woulfe's bottles, or all the carboys of 

 the front range may be placed in communication with one another, while the last car- 

 boy at one end is joined to the first of the second range ; and thus in succession. They 

 must be half filled with cold water ; and when convenient, those of the front row at 

 least, should be plunged in an oblong trough of running water. The acid which con- 

 denses in the carboys of that row is apt to be somewhat contaminated with sulphuric 

 acid, chloride of iron, or even sulphate of soda ; but that in the second and third will 

 be found to be pure. In this way 100 parts of sea-salt will yield 130 parts of muriatic 

 acid, of sp. gr. 1*19; while the sulphate of soda in the retort will afford from 208 

 to 210 of that salt in crystals. 



It is proper to heat all the parts of the cylinders equally, to insure the simultaneous 

 decomposition of the salt, and to protect it from the acid ; for the hotter the iron, and 

 the stronger the acid, the less erosion ensues. 



Some manufacturers, with the view of saving fuel by the construction of their fur- 

 naces, oppose to the flame as many obstacles as they can, and make it perform numerous 

 circulations round the cylinders ; but this system is bad, and does not even effect the 

 desired economy, because the passages, being narrow, impair the draught, and become 

 speedily choked up with the soot, which would be burned profitably in a freer space ; 

 the decomposition also, being unequally performed, is less perfect, and the cylinders 

 are more injured. It is better to make the flame envelope at once the body of the 

 cylinder ; after which it may circulate beneath the vault, in order to give out a portion 

 of its heat before it escapes at the chimney. 



The fire should be briskly kindled, bu]b lowered as soon as the distillation com- 



