Cooley's Cyclopaedia of Practical Receipts Volume Ii Part 217

Since the magnesium oxalate is always obtained of the same composition and in the same quant.i.ty, it is sufficient to determine its weight once for all, and to take each time the previously common amounts of common salt.

The acid need not be weighed either; it must be added in just sufficient quant.i.ty to destroy the milky appearance which the mixture first a.s.sumes.

The reaction is as follows:

MgC_{2}O_{4} + HCl + NaCl = NaHC_{2}O_{4} + MgCl_{2}

Magnesium + Hydrochloric + Sodium = Sodium Magnesium oxalate. acid. chloride. binoxalate. chloride.

The crystalline powder of sodium binoxalate is transferred to large draining filters, washed with water until the acid solution of magnesium chloride is removed, and worked up, as below described, while still moist.

The acid solution of magnesium chloride is made use of several times in succession as so much hydrochloric acid, together with a quant.i.ty of fresh acid sufficient for the reaction. Finally, when the magnesium chloride has inconveniently acc.u.mulated, it is worked up by itself into magnesia and hydrochloric acid.

2. In order to obtain the soda, the sodium binoxalate is brought together with an equivalent quant.i.ty of magnesium carbonate and water in a tight cask. As soon as the remaining air has been nearly expelled by the generated carbonic acid gas, the cask is closed, and a stirring mechanism set in motion.

A pressure gauge attached to the cask indicates a gradual rise of the pressure to two atmospheres, but, on continual stirring, this diminishes, until, finally, the gauge stands again at 0. The cask now contains a concentrated solution of sodium bicarbonate, and a precipitate of magnesium oxalate, which latter, being coa.r.s.ely granular, is easily separated from the liquid, and is used over again, after was.h.i.+ng, for a new operation.

The solution of sodium bicarbonate is boiled for a short time with magnesia, obtained in distilling magnesium chloride, and both are thereby converted into simple carbonates. Both reactions are shown in the following scheme:

1. NaHC_{2}O_{4} + MgCO_{3} = NaHCO_{3} + MgC_{2}O_{4}

Sodium + Magnesium = Sodium Magnesium binoxalate. carbonate. bicarbonate. oxalate.

2. 2NaHCO_{3} + MgO = Na_{2}CO_{3} + MgCO_{3} + H_{2}O

Sodium + Magnesia. = Sodium + Magnesium + Water bicarbonate. carbonate. carbonate.

As the solution of sodium carbonate, after concentration to 40B., is incapable of dissolving or retaining in solution any sodium oxalate, it follows that the whole of the oxalic acid is recovered. The magnesia which is required for the purpose is obtained by distilling magnesium chloride, which thereby splits up into hydrochloric acid and magnesia. One half of the latter receives, as we have seen, its carbonic acid by boiling with sodium bicarbonate; the other half is placed, whilst still moist, upon trays in great wooden closets, through which the gases of the furnace pa.s.s, and is thereby carbonated. The process may also be so modified that the sodium binoxalate is first decomposed by caustic magnesia, and that magnesium carbonate is afterwards added.

The whole mixture is then transferred to a stirring cask, provided with openings for the pa.s.sage of cooled furnace gases, whereby the caustic soda present is very soon carbonated.

3. As soon as a large quant.i.ty of magnesium chloride solution has acc.u.mulated, it is tested as follows:--A small sample is mixed, while boiling, with magnesium oxalate, as long as the latter is dissolved, and then allowed to cool. There should be no crystalline deposit of sodium binoxalate formed, a proof that the solution does not contain any sodium chloride in excess, and is fit for distillation. It is first neutralised by adding some more magnesia, and evaporated over a naked fire in large kettles to a doughy consistence, short of driving off the hydrochloric acid. It is then transferred into the ordinary soda furnace, where it is distilled with a moderate fire. The eliminated hydrochloric acid is condensed in the usual manner.

The residuary ma.s.s should not be heated red hot, so as not to impair its porosity or its ready affinity for carbonic acid. If, however, the first-mentioned test shows the magnesium chloride to contain sodium chloride the whole ma.s.s must be mixed with magnesium oxalate, and after removal of the precipitated sodium oxalate, saturated with magnesia and distilled. The same process, in all its details, may also be employed for the manufacture of pota.s.sa and its carbonate.

4. Another method of manufacture of commercial soda is by treating the mineral cryolite (a double fluoride of sodium and aluminium) with either caustic, or hydrate of lime. The results of the reaction are caustic soda, sodium aluminate, and calcium fluoride.

The aluminate and caustic soda being both soluble in water, a stream of carbonic acid is pa.s.sed through the solution containing them, whereby all the soda becomes converted into carbonate, whilst the alumina is thrown down as an insoluble precipitate. In the wet way, if enough hydrate of lime be employed, all the soda may be obtained in the caustic condition.

This process is largely used in Germany. Various other processes for the manufacture of commercial soda have been devised, some of which are still followed, whilst others, being impracticable, have collapsed.

Mr Kingzett, in his work on the alkali trade, has described most of them.

When anhydrous carbonate of sodium is required (SODae CARBONAS EXSICCATA, B. P., Ph. L.; SODae CARBONAS SICCATUM, Ph. E. & D.), the crystallised carbonate is heated to redness, and, when cold, powdered.

_Prop., &c._ Carbonate of sodium forms large, transparent, oblique rhombic prisms, which, as ordinarily met with, and of the formulae Na_{2}CO_{3}.10Aq; but by particular management may be had with fifteen, nine, seven, or sometimes with only one molecule of water of crystallisation (Fownes); it is soluble in twice its weight of water at 60, and less than an equal weight at 212 Fahr. As a medicine it is deobstruent and antacid, and is given in doses of 10 to 30 gr. It is also, occasionally, used to make effervescing draughts. When taken in an overdose it is poisonous. The antidotes are the same as for carbonate of pota.s.sium. The crude carbonate is largely employed in the manufacture of soap, gla.s.s, &c.

Fifty three gr. of the dried carbonate are equal to 143 of the crystallised salt. The medicinal properties of both are similar. It has, however, the disadvantage of being difficultly soluble in water.

The ordinary carbonate of sodium generally contains either sulphates or chlorides, or both; and these may be detected as under CARBONATE OF POTa.s.sIUM. "When supersaturated with nitric acid, it precipitates only slightly, or not at all, chloride of barium or nitrate of silver; and 143 gr. require at least 960 grain-measures of solution of oxalic acid" (B.

P.). At a high temperature 100 gr. lose 625 gr. of water.

=Sodium, Bicarbonate of.= NaHCO_{3}. _Syn._ SESQUICARBONATE OF SODA, SODae BICARBONAS (B. P., Ph. L., E., & D.). This salt can be prepared in exactly the same manner as the corresponding salt of pota.s.sium. Another method is as follows:--Take of crystallised carbonate of sodium, 1 part; dried carbonate of sodium, 2 parts (both in powder); triturate them well together, and surround them with an atmosphere of carbonic acid gas, under pressure; let the action go on until no more gas is absorbed, which will generally occupy 10 to 14 hours, according to the pressure employed, then remove the salt, and dry it at a heat not above 120 Fahr.

_Prop., &c._ A crystalline white powder; it is soluble in 10 parts of water at 60 Fahr., but it cannot be dissolved in even warm water without partial decomposition; it is more pleasant tasted and more feebly alkaline than the carbonate of the same base. When absolutely pure it does not darken turmeric paper, or only very slightly. The dose is from 10 to 40 gr., as an antacid and absorbent. It is much employed in the preparation of effervescing powders and draughts, for which purpose

20 gr. of commercial bicarbonate of sodium ------------------/--------------------/ are taken with /------------------/--------------- 18 gr. of crystallised tartaric acid;

17 gr. of crystallised citric acid; or

1/2 fl. oz. of lemon juice.

The quant.i.ty of bicarbonate any given sample contains may be approximately determined by well was.h.i.+ng 100 gr. of the salt with an equal weight of water, and filtering the solution. The residuum left upon the filter, dried at a heat of 120 Fahr., and weighed, gives the per-centage of pure bicarbonate of sodium present (very nearly). The solution of this in water will give only a very trifling white precipitate with corrosive sublimate; whilst the filtered portion, which was used to wash the salt, will give a red one, if it contains the simple carbonate of sodium.

=Sodium, Chloride of.= NaCl. _Syn._ SODII CHLORIDUM (B. P., Ph. L., & D.), SODae MURIAS (Ph. E.), L. This important and wholesome compound appears to have been known in the earliest ages of which we have any record. It is mentioned by Moses (Gen. xix, 26), and by Homer in the Iliad (lib. ix, 214). In ancient Rome it was subjected to a duty (_vectigal salinarium_); and even at the present day a similar tax furnishes no inconsiderable portion of the revenue of certain nations. Common salt forms no small portion of the mineral wealth of England, and has become an important article of commerce in every part of the known world. The princ.i.p.al portion of the salt consumed in this country is procured by the evaporation of the water of brine springs. It is also prepared by the evaporation of sea-water (hence the term 'sea-salt'), but this process has been almost abandoned in England, being more suited to hot dry climates or to very cold ones.

_Var._ BAY SALT; SAL MARINUS, SAL NIGER; imported from France, Portugal, and Spain, and obtained from sea-water evaporated in shallow ponds by the sun; large-grained and dark-coloured.--BRITISH BAY SALT, CHEs.h.i.+RE LARGE-GRAINED S.; by evaporating native brine at a heat of 130 to 140 Fahr.; hard cubical crystals. Both of the above are used to salt provisions for hot climates, as they dissolve very slowly in the brine as it grows weaker. CHEs.h.i.+RE STOVED SALT, LUMP S., BASKET S.; obtained by evaporating the brine of salt springs; small flaky crystals.--LONDON'S PATENT SOLID SALT; Ches.h.i.+re rock salt, melted and ladled into moulds.--ROCK SALT, FOSSIL S.; SAL GEMMae, SAL FOSSILIS; found in mineral beds in Ches.h.i.+re; has commonly a reddish colour; chiefly exported for purification.

_Prop._ Pure chloride of sodium is fixed in the air; crystallises in anhydrous cubes, which are often grouped into pyramids or steps; dissolves in about 2-1/2 parts of water at 60 Fahr.; its solubility is not increased by heat; it is slightly soluble in proof spirit; insoluble in alcohol; decrepitates when heated; fuses at a red heat, and volatilises at a much higher temperature.

_Pur., &c._ The common salt of commerce contains small portions of chloride of magnesium, chloride of calcium, and sulphate of calcium; and hence has commonly a slightly bitter taste, and deliquesces in the air. To separate these, dissolve the salt in 4 times its weight of pure water, and drop into the filtered solution, first, chloride of barium, and then carbonate of sodium, as long as any precipitate falls; filter, and evaporate the clear fluid very slowly, until the last crystallises, which is pure chloride of sodium. ('Thomson's Chem.,' ii, 377.) For medical purposes the Ph. E. orders the salt to be dissolved in boiling water, and the solution to be filtered and evaporated over the fire, skimming off the crystals as they form, which must then be quickly washed in cold water, and dried. A solution of pure salt is not precipitated by a solution of carbonate of ammonium, followed by a solution of phosphate of sodium; a solution of 9 gr. in distilled water is not entirely precipitated by a solution of 26 gr. of nitrate of silver. (Ph. E.)

_Uses._ Common salt is stimulant, antiseptic, and vermifuge, and is hence employed as a condiment, and for preserving animal and vegetable substances. It is also occasionally used in medicine, in clysters and lotions.

=Sodium, Dried Sulphate of.= _Syn._ SODae SULPHAS EXSICCATA, EFFLORESCED GLAUBER SALT. Expose the crystals to a warm dry air till they fall into powder. They lose half their weight. The dose is reduced in like proportion.

=Sodium, Effervescing Citro-tartrate of.= _Syn._ SODae CITRO-TARTRAS EFFERVESCENS. (B. P.) _Prep._ Mix thoroughly, powdered bicarbonate of soda, 17 oz.; tartaric acid, 8 oz.; and citric acid, 6 oz.; place in a dish or pan of suitable form, heated to between 200 and 220 Fahr., and when the particles begin to aggregate, stir a.s.siduously till they a.s.sume a granular form. By means of suitable sieves separate the granules of uniform and most convenient size. Preserve in well-closed bottles.

=Sodium, Ethylate.= Prepared as POTa.s.sIUM ETHYLATE, subst.i.tuting sodium for pota.s.sium. Properties similar to ethylate of pota.s.sium.

=Sodium, Hydrate of.= NaHO. _Syn._ HYDRATE OF SODA, SODIUM HYDRATE, CAUSTIC SODA; SODae HYDRAS. _Prep._ Exactly in the same manner from carbonate of sodium as pota.s.sium hydrate is prepared from carbonate of pota.s.sium.

The 'Pharmaceutical Journal'[177] states that a pure hydrate of sodium is now manufactured from metallic sodium by the following method:--A deep silver vessel, of a hemispherical form, and capable of holding about four gallons of water, is employed. Into this vessel, which is cooled externally with a current of cold water, is placed a very little water, and upon the water is placed a cube of metallic sodium, of about half an inch in diameter.

[Footnote 177: 3rd series, i, 65.]

The vessel is made to revolve, so as continually to bring fresh portions of liquid into contact with the metal, and by this means explosion is avoided. When the first cube of metal has dissolved, and yielded a thick syrupy liquid, a little more water and a second cube of metal are added, and the reaction allowed to take place, as before, the vessel being kept in motion all the time. In this manner several pounds of sodium may be worked up into soda.

The thick syrup so resulting is next evaporated down, heated to redness, fused, and poured into a mould.

Inasmuch as the price of sodium is five s.h.i.+llings a pound, the yield of soda from 1 lb. of metal being about 1-3/4 lb., it is plain that the alkali so prepared must be cheap.

The danger of explosions (which, however, are not likely to occur if proper care is taken) necessitates the employment of skilled labour in this manufacture, and const.i.tutes a very serious drawback to the commercial success of the process.

Greyish, semitranslucent, deliquescent ma.s.ses, very soluble in water, and bearing a very great resemblance to the corresponding pota.s.sium compound.

=Sodium, Hypochlo"rite of.= _Syn._ CHLORINATED SODA, CHLORIDE OF SODA; SODA CHLORINATA, L. _Prep._ (Dr Christison.) Dried carbonate of sodium, 19 parts, are triturated with water, 1 part, and the mixture placed in a proper vessel, and exposed to the prolonged action of chlorine gas, generated from a mixture of chloride of sodium, 10 parts; binoxide of manganese, 8 parts; sulphuric acid, 14 parts; (diluted with) water, 10 parts.

=Sodium Hypophosphate.= See PHOSPHORUS.