698 



SODA AND SODA COMPOUNDS. 



The chlorine gas evolved being passed, along 

 with an equivalent proportion of sulphurous 

 acid gas (from burning ulphur or pyrites) and 

 with steam, through a condenser filled with 

 coke, chlorhydric and sulphuric acids at the 

 same time result ; and these are afterward sep- 

 arated by distillation. Amer. Jour, of Science, 

 vol. xxxvi., September, 1863. 

 ; Kopp's Soda- Process, with Peroxide of Iron. 

 In the year 1777, M. Malherbe, a Benedictine 

 monk, proposed a method of producing car- 

 bonate of soda by acting on the sulphate of the 

 same base by means of charcoal and iron. This 

 process has in its essential features been re- 

 vived more recently by M. Emile Kopp, of 

 Strasburg, and has been brought into practice 

 at least in some English manufactories. In its 

 present form it consists substantially in decom- 

 posing the sulphate of soda by a mixture of 

 carbon and peroxide of iron, the three mate- 

 rials being in the proportion of 125, 55, and 80 

 kilogrammes, calcining the mixtures, and follow- 

 ing with " delitation " (exposure to air and 

 moisture), and finally, lixiviation. With an 

 impure sulphate, the other ingredients should 

 be proportioned to the quantity of pure dry 

 sulphate of soda present. The peroxide of iron 

 should be as pure as may be. weighed dry, and 

 in fine powder ; or it may be replaced with 

 carbonate of iron (spathic iron), or magnetic 

 oxide or iron-filings, provided the proportion 

 cf iron present in any case be such as to form a 

 sulphide (FcS) with all the sulphur of the sul- 

 phate. The mass is best calcined by using a 

 furnace with two or three stories : when in the 

 last and hottest of these it has softened, giving 

 off a yellow flame, and becoming homogeneous, 

 it is drawn oft', still red, into boxes on wheels, 

 and solidifies to a black, porous mass. In this 

 condition it is not well acted on by water ; but 

 the blocks, being exposed to air and moisture 

 under a shed, rapidly absorb oxygen, water, 

 and carbonic acid, and in course of some hours 

 fall_ to a pulverulent, reddish mass a change 

 which M. Kopp sometimes aids by another, 

 termed by him " carbonation." Pulverizing 

 the crumbled mass fine, a grayish powder is 

 obtained, and which is then sifted. 



The lixiviation is rapid, being performed 

 either by filtration or decantation, and with 

 water at from 30 to 40 0. Crystallization oc- 

 curs in 24 to 48 hours, without concentration 

 [the product being a highly pure carbonate 

 of soda]. The residue, again filtered and dried, 

 burns below 100 C., its sulphur being utilized 

 in the production of sulphuric acid, and per- 

 oxide of iron regenerated and used again. The 

 latter, indeed, gradually becomes impure, and 

 must finally be replaced by fresh oxide. The 

 sulphur, however, converted into acid, and 

 made to act on fresh portions of salt, is re-used 

 indefinitely. Amer. Jour, of Science, vol. xxi., 

 January, 1856. 



Soda- Processes with Baryta, and its Salts. 

 In the same number of the Technologists 

 (December, 1864) with his article previously 



quoted. M. E. "Wagner has another paper, anc 

 of some length, on the processes for soda spe- 

 t cially involving the use of caustic baryta or cer- 

 tain baryta-salts. Of these, the most successful 

 appears to be that by decomposition of sul- 

 phate of soda ly caustic baryta, patented in 

 England by Fuller in 1819, and by Samuel in 

 1838, and later recommended on the Con- 

 tinent by M. Anthon, of Prague, in 1840, and 

 by MV G. Hoffacker, of Stuttgard, in 1863. The 

 author states that in his own experiments he 

 has effected an easy and complete decomposi- 

 tion of sulphate of soda by caustic baryta, and 

 that at all degrees of concentration and of tem- 

 perature ; and he is led to coincide in the opin- 

 ion recently expressed by Prof. Ho'fmann, that 

 a cheap and plentiful supply of baryta, could 

 this base be so produced, would work a revolu- 

 tion in the business of fabricating soda. 



Soda-Processes ly Direct Action on Com- 

 mon Salt. In regard to these, little needs be 

 said in this place. In the process of Mr. Samuel, 

 a concentrated solution of sea-salt is treated 

 with excess of oxalic acid, the results being 

 chlorhydric acid and an insoluble binoxalate of 

 soda; and on boiling the latter with milk of 

 lime, caustic soda and oxalate of lime are ob- 

 tained. The chief difficulty hitherto has been 

 in the want of an economical mode of recover- 

 ing the acid, for re-use, from the lime-salt. 



Propositions have been at several times made, 

 looking to a decomposition of common salt by 

 steam at high temperatures (of course, under 

 pressure, in strong vessels) ; but the resulting 

 caustic soda and chlorhydric acid tend to de- 

 compose again at lower temperatures, and be- 

 fore the soda can be separated, with reproduc- 

 tion of the original materials. The introduction 

 of a third body such as will at once combine 

 with the soda forming, and in a non-volatile 

 compound afterward readily decomposable, of- 

 fers a means of overcoming the difficulty refer- 

 red to ; and for such purpose alumina and 

 silica have been used. 



In Mr. Tilghman's process, precipitated 

 alumina is made, up into balls with chloride of 

 sodium ; and these are exposed to a current of 

 steam in a reverberatory furnace, strongly 

 heated. Chlorhydric acid and soda result ; tho 

 former is expelled, and the latter combines 

 with the alumina, from which, when cold, it is 

 again separated by means of a current of car- 

 bonic acid : the carbonate of soda is dissolved 

 out, and the alumina can be re-used. (UEE.) 



Mr. William Gossage, of Lancashire, patented 

 (July, 1862) a method of obtaining soda or pot- 

 ash from the corresponding chloride, and by 

 aid of silica or alumina, or both. Filling a suit- 

 able reservoir with fragments of one of these 

 earths (and which he terms u decomposing sub- 

 stances 1 ')) he passes through the interstices of 

 the mass the alkaline chloride in a state of 

 vapor, along with steam the whole being at a 

 high temperature : in the fabrication of soda, 

 the chloride of sodium being employed, silicate 

 or aluminate of soda, or both, as the case may 



