SODA AND CHLORINE RESIDUES, UTILIZATION OF. 



by combustion, in which it 

 may } --vapor and sulphurous acid gas 



(IIS + I'.O IK)-} -SO,), or, by properly dimin- 

 ishing the supply of nir, into water-vapor nnd 



ulphur (1IS + = IIO + S). In attempt- 

 ing the farmer comerMun, as for the sulphuric- 

 aci ! manufacture, tho excess of air require'.!, 

 introducing much nitrogen into the chambers, 



s a serious obstacle. It is best, therefore, 

 to burn the sulphydric acid for free sulphur, or 

 for sulphurous acid tho latter to be then util- 

 i.vd iu producing hyposulphites of soda and 

 lime, and sulphites or bisulphites of the same 

 or of alumina. These salts have various uses 

 in tho arts, the hyposulphites being employed 

 for destroying tho effect of chlorine, as a mor- 

 dant in certain cases, in the processes of 

 photography, in tho extraction of silver, etc., 

 while by means of the hyposulphite of lirno 

 the corresponding salt of certain other bases 

 can !>e formed. Methods of burning the sul- 

 phydric acid gas so as to secure at will either 

 one of tho results above stated, or so as to se- 

 cure at the same time both sulphur and sul- 

 phurous acid, and also those of preparing tho 

 salts named, are indicated in M. Kopp'a me- 

 moir. 



Tho liquid residuum from which the suc- 

 cessive extractions have been made is now 

 nearly neutral, containing chiefly chlorides of 

 iron, manganese, and calcium. The author 

 runs it into cisterns, and, by using the coarse 

 lime rejected in the manufacture of chloride 

 of lime, precipitates the oxides of iron and 

 manganese and a small quantity of their sul- 

 phides. After deposit of these, tho liquid is 

 quite neutral and cannot harm vegetation ; 

 while the chloride of iron still in solution de- 

 posits an insoluble iron-salt, and then only 

 some portion of the chlorides of manganese 

 and lime are left in the liquor. If even this 

 liquid should not be run into a stream, the au- 

 thor suggests that it may be evaporated to dry- 

 ness, the mixed chlorides being then fused in a 

 revcrberatory furnace. The mixture can be 

 used as a flux in puddling iron or steel, or in 

 improving bad cast-iron. A process is also de- 

 tailed, however, for freeing the liquor of tho 

 remaining salts named, by successive reactions. 

 A satisfactory statement of tho process of 

 . Townscnd and Walker, and which ap- 

 to be in use in connection with some 

 nglish chlorine works, has not been met with. 

 It i> said, however, to be in many essential 

 features identical with that of M. Kopp above 

 described, an important difference being that 

 the English process does not attempt to utilize 

 the sulphur evolved in the sulphydrie acid gas. 

 A soniewliat close affinity between M. Kopp's 



>ses and those of M. Fabre is also discov- 

 erable. Tho latter does utilize the sulphydrio 

 acid, but, in one method, by burning it, either 

 by itself or by directing it into the h're of burn- 

 ing pyrites, for the production of sulphuric acid; 

 and in another method, by directing it into wa- 

 ter holding tho sulphurous acid of the products 



E 



of combustion of pyrites, where, as the author 

 claims, aiding tho effect by pressure or agita-. 

 tion, a reaction occurs in which water is gen- 

 erated and tho sulphur of both tho sulphurous 

 and sulphydric acids precipitated. To evolve 

 the sulphydric acid in the first place, M. Fabre 

 acts upon the sulphide of calcium of tin- 

 dues by the chlorhydric acid set free during 

 tho fabrication of crude soda. Indeed, M. 

 Kopp acknowledges the general similarity of 

 his own to the processes for the like purpose 

 of certain other chemists ; and he states that 

 he has not professed to give new modes of 

 treatment of the residues in question, but 

 rather to present in detail tho entire system 

 of measures by means of which, with the least 

 expenditure of labor and with tho greatest 

 economy, the whole of such residues can be 

 rendered inoffensive, and be made to yield 

 with profit products which can be utilized. 



M. Kopp's memoir closes with an account 

 of modes of utilizing soda wastes, taken by 

 themselves, and without the use of chlorhydrio 

 acid or chlorine residues. This latter and sim- 

 pler form of treatment he regards as indispen- 

 sable to the purpose of converting the entire 

 waste of large alkali works ; since his process 

 previously given, though effectual, is adequate 

 to the disposal of onlv part of such accumu- 

 lation. The heaps which remain offend the 

 smell with sulphydric acid gas only in foggy 

 and moist weather; but the liquid drainings 

 from the heaps, yellowish in color, strongly 

 alkaline, rich in sulphur-compounds, and giv- 

 ing off to the air the gas already named, con- 

 stitute a real nuisance, and, running freely into 

 streams, destroy fish. 



If a heap of soda-waste be simply left with- 

 out addition for some years, the drainings from 

 it continuing and also the action of air and 

 moisture upon its materials, the escaping liquid 

 will gradually change in character, becoming 

 colorless, neutral, and containing only sulphate 

 of lime. The heap, meanwhile, changes from, 

 a dark gray to a yellowish white ; and it is 

 now found to consist largely of sulphate and 

 carbonate of lime, with traces of sulphate and 

 hyposulphite of soda, and of chloride of sodium, 

 oxide of iron, alumina, silica, etc., and a small 

 amount of free sulphur. In this condition tho 

 material is no longer hurtful to vegetation, but 

 proves an excellent ameliorator of silicious or 

 clay soils in which lime is deficient. But the 

 process may bo expedited. In proportion to 

 tho amount of the waste at chemical works 

 there will be produced also a quantity of coal 

 slag and of broken bricks. These may to- 

 gether bo deposited along tho heaps of waste 

 at distances of four or five yards, in rows ono 

 yard high and broad, and tho waste tilled in 

 between and over them, until it is proper or 

 convenient to lay fresh rows of the broken 

 material. The open spaces in these rows will 

 serve as channels along which atmospheric air 

 circulates, so as in less time to act upon the 

 whole mass, oxidizing the sulphide of calcium. 



