SODA SALTS.

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Chloride of Sodium.

Common salt, or chloride of sodium (NaCl), finds but few diredt appli-cations in the branch of industry under consideration.

Hypochlorite of Soda.

Hypochlorite of soda, NaO.CIO, also known as chloride of soda, serves asa bleaching agent and in the preparation of several colours. It is preparedby the decomposition of chloride of lime with carbonate or with sulphate ofsoda, or by passing chlorine into a solution of carbonate of soda.

The bleach liquor is of a yellow colour, with a strong odour of hypochlorousacid.

Hypochlorite of soda can be subjected to the same tests as to strength ashypochlorite of lime, and we shall revert to the subjedt when treating ofChlorimetry. A hypochlorite of soda bath at g° B. is obtained when 6J lbs. ofhypochlorite of lime at 8° B. are added to i£ lbs. crystallised soda. It canbe employed in the bleaching of white grounds upon brilliantly coloured cottonfabrics.

Phosphate of Soda.

Phosphate of soda, NaOjPOj, is but seldom used in calico-printing. Itpartakes of the charadler of a weak alkali, and is used as a solvent for ladlarine.As an alkaline salt it causes the precipitation of a greater quantity of ironfrom citrate or sulphate solutions of iron mordant, and hence gives rise to adepth of colour known as a double shade.

Permanganate of Soda.

Permanganate of soda, Na 0 ,Mn 2 0 7 , which is employed as often as per-manganate of potash for technical purposes, is of high value as an oxidisingagent for bleaching or for disinfedting. It may be obtained by fusing in aniron vessel ro parts of caustic soda with r part of nitrate of potash, to whichis added in small portions on an iron spatula 6 parts of peroxide ofmanganese. The fused mass is lixiviated with boiling water, and the saltcrystallised out by evaporation. A crude permanganate may be obtained byheating to redness with access of air a mixture of 2 parts of nitrate of sodawith 1 part of peroxide of manganese.

Tungstate of Soda.

Tungstate of soda is employed in the fixation of logwood pigments.In colouring sheep’s wool it is substituted for tin salts.

Tungstate of soda may be prepared by heating 5 parts of tungstic acidwith 5 parts of calcined soda in an iron capsule; the tungstate is obtained bydissolving the fused mass in water, and then concentrating the solution byevaporation.

Hyposulphite of Soda.

This salt is used in fixing aniline greens upon the fibre, and is hence knownm the trade as “ green mordant.” In conjunction with salts of copper it hasbeen employed in the production of so-called “ argentine ” effects, a thin filmof sulphide of copper being deposited on the fibre.

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