C H E M I C A L S

Dendritic Salt Goes Into Production Morton will market salt with star-shaped crystals, foresees their use in dye and detergent industries

Morton Salt, Chicago, 111., will soon be offering a new type of salt. Un­like regular vacuum or flake salt, it has a s tar like crystal structure. The new sodium chloride is called dendri­tic. It is made by treating brine with a chemical that causes the crystals to grow at the corners instead of at the faces and edges, according to John M. Page, Morton's technical service man­ager.

Currently used in developmental quantities as a bulking agent in tex­tile dyes, dendritic could find applica­tions in industrial detergents and soaps, explosives, dry bleaches. The company is now making the salt at its Silver Springs, N.Y., plant, plans to start furnishing it commercially on June 1. Price will be on a par with other high purity salts, Morton says.

Dendritic salt is produced from chemically purified brine by a vacuum evaporation process. The process was developed in England by Imperial Chemical Industries, Ltd., which was looking for a low bulk density salt. Morton has been negotiating with ICI, now has an exclusive license for mak­ing dendritic salt in the U.S.

Controlled Growth. In the con­ventional vacuum evaporation method for making salt, Mr. Page explains, the brine is treated with sodium hydroxide and sodium carbonate to remove cal­cium and magnesium impurities.

Then it passes to vacuum pans, where hot steam brings the brine to boiling. Salt crystals form and remain in sus­pension until they grow large enough to sink to the bottom of the pan, where they are pumped off as a slurry. This slurry is washed and the crystals filtered out. Finally, the salt is dried, screened, and packaged.

To produce dendritic salt, the con­ventional process must be modified at

the crystal growth stage. Here, Mor­ton introduces sodium ferrocyanide in aqueous solution to the salt as it crys­tallizes in the vacuum pans. The chemical is adsorbed on the faces of the vacuum salt, retarding growth at the faces and edges. Growth can only take place then at the corners of the crystal, Mr. Page points out. As a re­sult, the crystals are 3 dimensional, have a branched or starlike appear­ance.

The finished product is finely granu­lated like vacuum salt; yet, like flake salt, it has relatively low weight per unit volume. Its bulk density ranges from 55 to 60 lb. per cu. ft., compared to 71 to 77 for vacuum salt and 45 to 65 for flake. Purity is 99.9% sodium chloride, with less than 100 p.p.m. cal­cium and magnesium impurities. Den­drite's properties include:

• Relatively high specific surface which gives fast solubility.

• Good blending ability.

• Large capacity for absorbing moisture without becoming wet.

• Good storing quality without caking.

Shape Pays Off. Dendritic salt is now used in developmental quantities in the textile industry for dry blending or standardizing concentrated dyes. In this application, it is mixed with the dye—frequently in ratios as high as 1:1. The mixture is weighed out and ap­plied as a percentage of the textile materials' weight. Since the dye is used in this way, any variation in con­centration of the dry mixture would greatly affect the resulting color on the textile.

Here is where dendritic has several advantages over cube or flake salt, Mr. Page says. For one, dendritic blends well, doesn't separate out as easily as conventional salts, even in handling and shipping. This property prob­ably stems from the shape of the crys­tal. Dendritic has an irregular sur­face, doesn't reflect light like cube salt. So it doesn't give what the dye­ing industry calls the "salt and pepper effect."

The salt's properties of free flow and rapid water solubility are also big advantages to textile dyers. Dyes in­corporated with dendritic store much better than those containing cube, or flake salts, according to Mr. Page. Also, dendritic is a fragile salt, thus processes well in blending or mixing equipment.

Morton foresees many more appli­cations for dendritic. Potential uses include bulking agents in industrial detergents and soaps or in dry bleaches, most of which now use vacuum salt. It could replace flake salt now used in explosives.

BRIEFS

Three organic intermediates have been added to the line of Pfister Chemical Works, Ridgefield, N.J. They are 2,4,5-trichloronitrobenzene, a yellow crystalline solid, insoluble in water and alcohol but soluble in carbon disulfide; 2,4-dimethoxy-5-chloiOnitrobenzene, a light yellow powder with a melting point range of 121° to 124° C. and soluble in chloroform and ether; and yg-naphthylamine, white to reddish flakes with a minimum purity of 98.5% and a melting point range of 110° to 112° C. C I

CRYSTAL STRUCTURES. Although magnifications differ slightly, the photomicro­graphs clearly indicate the difference in structure between Morton's star-shaped dendritic (left) and conventional salt crystals

48 C & E N M A Y 1, 1961

Butonate, 0,0-dimethyl-2,2,2-tri-ehloro-1-n-butyryl-oxyethyl phospho-nate, an insecticide for use against household insects, can be formulated as an oil spray, an emulsion, or a wet-table powder. Developed by Wiscon­sin Alumni Research Foundation, it will be manufactured and distributed by Prentiss Drug and Chemical Co., New York, N.Y. Butonate has very low mammalian toxicity, and its rela­tively light odor is easily masked, the company says. C 2

Two sheeting grade polypropylenes, with a melt index of 0.6, are available from En jay Chemical, New York, N.Y. Escon 502 is a general purpose sheet­ing grade; Escon 522 is a long-term, heat aging grade, designed for service at high temperatures for long periods. They are expected to find use in fabri­cating objects with large surface areas.

C 3

Column packing for gas chromato­graphic analysis of triglycerides is available from Applied Science Lab­oratories, Inc., State College, Pa. In addition, three products have been added to the company's line of high purity (99%) fatty acid derivatives. They are ethyl stéarate, ethyl palmi-tate, and ethyl caproate, all of which are for use as gas chromatography standards. C 4

Acetophenone, technical grade, with a purity of 97.1% is being produced by Union Carbide Chemicals, New York, N.Y. This new grade will allow cost savings in many noncritical ap­plications, such as the manufacture of corrosion inhibitors, resins, and dyes, Carbide says. C 5

Gluconic acid and sodium gluconate are now available in commercial quan­tities from Industrial Biochemicals, Inc., Edison, N.J. The sodium glu­conate is spray dried, comes as free-flowing, low dusting granules that dis­solve rapidly. The gluconic acid is available as a 50% yellow solution.

C 6

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M A Y 1, 1961 C & E N 49

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