183 



SALSEPARIN. 



SALTS. 



254 



being often uncertain and varying in the same piece of cloth, in many 

 spot* being foxif, as it is technically termed. 

 SKI'ARIN. [SMILACIN.] 



S\LT. [SODA; SODIUM: MANURE.] 



SA LT CAKK. [SODU'M ; Sulphate of.] 



SA l.T i >K SA'lTlty, an old name for acetate of lead. 



SA l.T UK SORREL. [OXALIC ACID. Sinoxalate of Puttah.] 



SALT OF TARTAR. [POTASSIUM: Carbonate of Potath.] 



SALT OF TIN. [Tin. Protochlinide of Tin.] 



SALT AN'I) SALT TRADE. The chemical nature of common 

 salt, as a chloride of sodium, is treated under SODIUM. The vast stores 

 of rock-salt and salt-brine in Cheshire and Worcestershire, whence 

 England obtains her supply, are described in the GEOO. Div., under 

 such headings as CHKSIIIRK, DROITWICII, NANTWICH, NOBTHWICH, &e. 

 A few additional details in this place are all that will be needed. 



A rocky bed is the source of nearly all our inland salt; but as sub- 

 trrnuiean streams flow over this bed and become saturated with salt, 

 the original form is changed. It is simply a question of manufactur- 

 ing convenience, whether to raise the solid salt and purify it by dis- 

 .1;, boiling, evaporating, &c. ; or to raise the liquid brine and 

 operate upon that. The salt-works adopt the latter course in most 

 part* of England ; but at Northwich they also operate upon a rocky 

 kind of salt, which is transparent and colourless, and is loosened by 

 blasting. There are other kinds of rock salt, much rougher and 

 darker. On many parts of the coast salt in obtained from sea-water, 

 at places called taitems; but as the salt would be too costly if evapo- 

 r.itt-d by heat, the makers mostly rely on the slow process of evapora- 

 tion liy exposure to the open air. At Lymington both methods are 

 combimil. 



In Cheshire the brine springs have been known and worked from 

 irly times, but the bed of salt whence the brine is obtained was 

 not known until about two hundred years ago. In the pita, the rock 

 loosened much in the same way as coal, by blasting and by the 

 pick, and is brought to the surface to be dissolved in water. The 

 brine springs in the valley of the Weaver mostly spring from a depth 

 varying from In to 60 yards. The brine is pumped by steam power 

 into large cisterns, where it is more completely saturated by an addi- 

 tion of rock salt. The brine then passe* through wooden troughs to 

 . aporating pans, large flat open vessels with flues underneath. 

 The evaporation, and the conversion into grains or crystals of salt 

 vary according as rommon salt, timed salt, jlatey salt, Jittery salt, &c., 

 are to be produced ; but in all, the crystals are allowed to form, and 

 are then removed to the drying house. The blocks of common salt 

 familiar in the shops are produced by transferring the crystals from 

 il.-- pan to wooden moulds, whence they are removed to be dried. 



Nearly the whole of the salt exported is made in Cheshire, and is 

 sent down the river Weaver, which comuiuuicates with the Mersey, 

 to Liverpool. The sources of supply are said to be inexhaustible ; 

 and latterly the salt-manufacturers have so far extended their works, 

 that the opening of new market* would be of the greatest advantage to 

 ih. in. The Staffordshire ruck-salt is chiefly exported from Hull, and 



i Worcestershire from the port of (Gloucester. 



A duty of 10*. per bushel was laid on salt in 1798, which in 1305 

 was increased to 15*. In 1823 this duty was reduced to 'it. ; and on 

 the 5th January, 1825, was wholly repealed. Salt used in the fisheries 

 was always duty-free, and in 1 -.1 the quantity so used was 2, -I"-;. '"_' 

 bushels ; and about 1 50,000 bushels, required by bleachers, was also 



from the duty. A duty of only 5.. . which was afterwards 



I to 'it. ''"/., was charged on salt used fur agricultural purposes. 

 During the existence of the duty, the retail price was 4J(/. per Ib. ; 



>w about {</. Salt is now used more largely than hitherto by 

 tin- i "or. and is employed in manufactures and in agriculture to an 



which it only compatible with cheapness. 



In 1 852 an estimate was nude that 300,000 tons of salt were used in 



nited Kingdom annually for domestic purposes, 200,000 tons for 



i.,. mure and manufactures, and 500,000 tons exported. In that year 



tli.- (.rices varied from 2. 6d. to 12. per ton. The aggregate value of 



the whole was set down at 350,OOW. In Cheshire only, in that year, 



.1 and 97 saltworks belonging to 47 proprietors, 



]raous, and an invested capital of I,IIIIII,<M.O/. In 



was believed to have risen from 1,000,000 tons 



to l.loii.oiiii toiiH annually, of which about one half is exported. If 



tin- above figures are correct, tbe domestic coiiiium]>tion must be far 



more than 1'. I'.-., per head, which was an estimate made several years 



ago. In 1858, the salt-main:; i Cheshire and Worcestershire 



i-ialited the government, praying that means might beado|,i.-d 



.lititing the consumption of liritixh salt in India and China. A 



:H.H li.id IH-.-H made in li* K>, by whii'h British salt was admitted 



under* >Ttain conditions into India; and tin- mem n dials asked for still 



more favourable conditions. As for China, they suggested that, in 



any treaty between the two countries, a demand should be mail. f..r 



.n of British salt, either free or under a small duty. The 



ire manufacturers have, in fact, more salt than they know what 



.'. it li ; and they are looking out for an extended market. At 



present, the two best customers are Calcutta and New Orleans, each of 



which tak. "id tons a-year. 



. N.TKK. (I'oTAHSIUM : Xilralf ;f P:,ta*h.} 



lit, originally re.-tii't d in its application to 



common salt, which it still means when used merely by itself, is now 

 applied to a vast number of substances which have in many cases few 

 properties in common. 



Common salt is the principal of a class composed of a metal and 

 such bodies as chlorine, iodine, bromine, and fluorine, and the radicals 

 of the hydracids, and which are included by Berzelius in his class of 

 haloid '-salts (from oAv, sea-salt, and d&os, form), because in constitution 

 they are analogous to sea-salt. The whole series of the metallic 

 chlorides, iodides, bromides, and fluorides, such as chloride oi sodium, 

 iodide of potassium, and fluor-spar, are, as well as the cyanides, sulpho- 

 cyanides, and ferrocyauides (though the three last are very differently 

 constituted from the former), included by Berzelius in his list of 

 haloid-salts. 



It was for many years admitted as an unquestionable fact that com- 

 mon salt was a compound of muriatic acid and of soda ; and hence it 

 was very commonly called muriate of soda. But it has been shown by 

 Davy, that the acid and alkali during their action on each other suffer 

 mutual decomposition ; and that while water is formed by the union 

 of the hydrogen of the acid with the oxygen of the alkali, the chlorine 

 of the former and the sodium of the latter unite to form chloride of 

 sodium. . It has since been proved that this occurs with all so- 

 called hydracidt, when they act upon metallic oxides : thus hydro- 

 chloric acid and soda give chloride of sodium and water, hydriodic 

 acid and aoda yield iodide of sodium and water, and hydrocyanic acid, 

 cyanide of sodium and water, &c. 



While then the hydracids, by the decomposition which they suffer, 

 do not yield hydro-salts with the metallic oxides, yet hydro-salts may 

 be formed by saturating these acids with the vegetable alkaloids ; for 

 example, hydrochloric and hydriodic acids yield respectively hydro- 

 chlorate and hydriodate of quinine, when made to act upon this base. 

 With ammonia hydrochloric acid forms the salt called sal-ammoniac ; 

 but these salts are analogous to the chlorides, chloride of ammonium 

 being formed by the conversion of the ammonia into ammonium, by 

 the transference of the hydrogen of the hydrochloric acid to the am- 

 monia, which is theoretically supposed to consist of one equivalent of 

 nitrogen and four equivalents of hydrogen, instead of one equivalent 

 of nitrogen and three equivalents of hydrogen, which exist in am- 

 monia. 



The oxy-mlti form another numerous and important class of com- 

 pounds : these are formed when an oxacid is made to combine with an 

 oxidised base; as, for example, when sulphuric acid unites with .soda, 

 the result being sulphate of soda. The sulphates of potash, lime, 

 mtgrmif, 4c., are similarly constituted; but a question has ari.-en 

 whether these salts are not also analogous . to the chlorides, in 

 containing a metal rather than an oxide ; thus, instead of supposing 

 that sulphuric acid, composed of one equivalent of sulphur and three 

 equivalents of oxygen, is combined with soda, formed of one equivalent 

 each of sodium and oxygen, it has been, and with much plausibility, 

 supposed that the oxygen is transferred to the sulphuric acid, forming 

 a compound which has never yet been isolated, consisting of one 

 equivalent of sulphur and four equivalents of oxygen, and that this is 

 combined with sodium. Professor Daniell proposed the name of 

 ojcytulpkion of sodium for such compound, while Professor Graham 

 denominates it a eid/i/i'ii-ij.rnlc composed of gulphat-oxyijen and 

 sodium. 



Another class of bodies has been described by Berzelius as coming 

 within the description of salts ; namely, the sulphur-salts. Electro- 

 positive sulphides, termed gitl/i/titr-base*, are usually the protosulphides 

 of electro-positive metals, and therefore correspond to the alkaline 

 bases of thooe metals; and the electro-negative sulphides, sulphur-acid*, 

 are the sulphides of the electro-negative metals, and are proportional in 

 composition to the acids which the same metals form with oxygen. 

 Thus sulpharsenious acid (AsS,) and sulpharseuic acid (AsS 6 ) combine 

 respectively with sulphide of potassium (KS) to form the sulphar- 

 sem'te and sulpuarseniate of potassium. These salts obviously corre- 

 spond with the arsenite and arseniate of potassium. Hence, if the 

 sulphur of a sulphur-salt were replaced by an equivalent quantity of 

 oxygen, an oxy-salt would result. 



in general properties the various classes of salts, and indeed the 

 individuals of the same class, differ as widely as possible ; some are 

 crystaUisable, others uncrystallisable ; they are colourless, and of 

 various colours ; sapid and insipid ; soluble and insoluble in water, 

 alcohol, and other menstrua ; volatile and fixed in the fire ; decom- 

 posable or undecomposable by the same reagent. 



Salts have been conveniently, though not quite correctly, divided 

 into alkaline, earthy, and metallic salts; for, strictly speaking, most of 

 the two former belong to the latter, and to these classes must be added 

 the ammoniacal salts and the salts of the vegetable alkaloids. Again, 

 salts constituted of the same elements may contain one or other in 

 excess ; thus soda and various other bases combine with three different 

 portions of carbonic acid. The first is the neutral carbonate, containing 

 one equivalent each of acid and of base ; the second contains one-halt' 

 more carbonic acid, and is called the sesqui- carbonate ; and the 

 third contains twice as much carbonic acid as the first, and is the 

 bi-carbouate. 



Super-salts are such as contain an excess of chlorine or of acids, and 

 sub-salts such as contain excess of base. Dr. Thomson has proposed 

 and it is very conveniently adopted in practice to describe the degree 



