SODA AND SODA COMPOl 





ion salt nti'l sulphate of ammonia ; from 

 .nd uluin (Coiistantin and Dnn- 

 '.!); from common salt ami sulpl: 



\'nii <1>T Hallcn); from common 



;' lime (Hudson ami ( 

 I'niiii common salt ami sulpL 

 Scheclf, I>i- I.iina): I'm m common 

 ,!id sulphate of copper, with production of 

 chin: from common s'llt ami pyrites, 



iai-1. Mc-dach) ; from 



comi; '1 sulphate of /inc; l>y cnleina- 



tiun of cnmmon salt with sulphate of lead ( Mar- 

 guerittci; fr.>in common salt and sulphate of 



I\'. Primarily acting on common gait by 

 oxide of 1. 'e, 1775); by carbonate of 



1 7s ! i ; l>y hydratcd lime (Guy- 

 ton nud Carny, 1780); by carbonate, or bicar- 

 f ammonia (Turck, Dyar and Hem- 

 ming, Schlosing); by oxalic acid (Kobcll, Sam- 

 hy tluosilicie acid, and then by caustic 

 Spilsl.tirg and Muughan, 1837; Kessler, 

 1858); by hydrate of alumina, prepared or 

 native (diaspoiv), then by carbonic acid or cry- 

 olite in the latter case, finally by lime (Tilgh- 

 t man, Tissicr); by silica and vapor of water, 

 then by carbonic acid (Vauquelin ; Gay-Lussao 

 and Thenard. 1809, etc.). 



V. With allite, and other soda-yielding sili- 



--hy calcining with lime (Do Fncbs); by 



litharge, then gaseous carbonic acid ; by fluoride 



.Icium, or by cryolite and sulphuric acid, 



ilicium as a fluoride. 



Outline of Leblanca Process. In this, two 

 independent steps are essential : the prepara- 

 tion of sulphate of soda from chloride of so- 

 dium, and decomposition of the sulphate into 

 the mixed mass containing the crude soda a 

 thinl, the purification of the crude soda into 

 the refined or crystalline article, or its conver- 

 sion into caustic soda, heing optional with tho 

 original manufacturer, since much of tho crude 

 produced is cither sold for use in that form 

 or taken for refining at separate works. Tho 

 It, or common salt, may be heated with 

 sulphuric acid (sp. gr., 1.6), taken in equal 

 iits, within two contiguous furna* 



1 and more highly heated of which 

 the mixture is directly transferred fur the com- 

 pletion of the process. Double decomposition 

 of the materials takes place, with production 

 of sulphate of soda and chlorhydric acid ; the lat- 

 ter, escaping in enormous \olmm s. is con 

 and secured by passing it into towers filled with 

 broken coke or stone, and over which water 

 is made to trickle. 



In the second stop, tho sulphate of soda, 

 dried and pulverized, is intimately mixed with 

 charcoal or coal, and chalk or limestone (car- 

 bonate of lime), both previously reduced to 

 powder and sifted. The proportions ditfer at 

 ditferent works: Ure gives, by weight, six parts 

 of sulphate of soda to seven of chalk and four of 

 coal. This mixture is fused in a reverheratory 

 furnace, and again in two stages: in tl 

 the prcparavory heating of the materials is 



effected ; in the socot.d t',c fusing and ' 



mass, which gives olV i-jiin-rom jets of blue 

 flame (burning carhonlr oxide), is to bo fre- 

 quently MiiT.-d and incorporated throughout, 

 and when the jets nf flamo begin to fade, to be 

 raked out into cast-iron moulds. The pi 

 i> the crude and impure soda, and is variously 

 known as "black balls." "ball alkali," "soda 

 ash," etc. The view presented l.y THE of tho re- 

 actions which occur, is as follows: first, much 

 of tho oxygen of tho sulphate of soda combines 

 with carbon, yielding the carbonic oxide gas 

 already referred to, and leaving a sulphide of 

 sodium ; and, secondly, this sulphide to a large 

 extent reacts with the carbonate of lirae, the 

 result so far being carbonate of soda and sul- 

 phide of calcium. The reactions are, however, 

 seldom, if ever, complete ; and from this cause, 

 together with the necessary presence of some 

 foreign matters in the materials used, the crude 

 alkaline mass as thus obtained isof more or less 

 variable, and always of complex composition. 

 Richardson has given the composition of the 

 black balls from works at Newcastle as, in 100 

 parts, carbonate of soda, 9.89 ; hydrate of (i. e^ 

 caustic) soda, 25.64 ; sulphide of calcium, 

 85.57; carbonate of lime, 15.67; sulphate of 

 soda, 3. 04; chloride of sodium, 0.60; sulphide 

 of iron, 1.22 ; silicate of magnesia, 0.88 ; carbon, 

 4.28 ; sand, 0.44 ; water, 2.17. In this sample, 

 however, the proportion of caustic soda is 

 unusually large, and that of carbonate of soda 

 unusually small, while free lime is not men- 

 tioned. Tho sulphide of calcium, itself spar- 

 ingly soluble in water, is rendered still less so 

 by the excess of lime which is commonly pres- 

 ent. (UsE.) It is this mixture of insoluble sul- 

 phide and oxide of calcium that has been gen- 

 erally, though it appears improperly, regarded 

 as forming a calcic oxysulphide. 



The purification or refining of the crude al- 

 kali is conducted either by washing or by lix- 

 iviation, with subsequent evaporation, and as 

 not differing very essentially from tho methods 

 of purifying saline substances generally, need 

 not here bo given at length. The reader is re- 

 ferred to lire's Supplement, or Millers Chem- 

 istry, for a description (with drawings) of the 

 ingenious method in use at some of tho works 

 for obtaining a concentrated soda-lye from tho 

 a.^h, by means of a succession of tanks at lower 

 and lower levels, and removing tho ash succes- 

 sively from the lowest to the highest of these. 

 In tho evaporating process, at a certain density 

 of tho lixivium, this may be set aside for crys- 

 tallization; or the evaporation may be con- 

 tinued to dryness, when tho result is the some- 

 what impure carbonate of soda, known as 

 sal-soda. This usually still contains a small 

 percentage of sulphide of sodium, from which 

 it is desirable to free it, and naturally more or 

 lc-s of caustic soda, by converting which into 

 carbonate a uniform product is obtained, and 

 tho weight at the same time increased. One 

 method of removing the sulphur, and at the 

 same time carbonating any caustic soda that 



