On Algin.

A New Substance Obtained from Some of the Commoner Species of Marine Algae.


The main object of the present paper is to introduce a new seaweed industry, the present uses for this substance being very limited, and in some cases a great loss of useful material occurs in the preparation of the products for commercial purposes. In the process recommended by the author, the seaweed is first macerated with cold water by washing in a number of vats in turn, by which means about one-third of the weight of the sea-weed is removed. The weed is now bleached with chlorinated lime-water, treated with acid, and washed. To extract the algin, it is acted on with one-tenth of its weight of sodium carbonate for 24 hours in the cold, and is then carefully heated, filtered, and evaporated: the residue on the filter is cellulose, and can be used in the manufacture of paper. The result of this treatment of laminaria is the separation of the sea-weed into the following parts: Moisture 20, extracted by water 30, extracted by acid 5, extracted by sodium carbonate (algin) 35, and cellulose 10 per cent.

When evaporated to dryness the aqueous extract forms a viscid mass, consisting of the salts mixed with a saccharine matter resembling mannite in appearance; this precipitates Fehling's solution to the extent of 15 per cent. glucose; it does not ferment, and would hence be very useful, but as yet there is no process for separating it from the salts. The whole mass is therefore carbonized and treated in the usual manner for separating the iodine and salts. Analysis of mixed samples of the salts yielded the following results:

Fucus vesiculosus. Laminaria stenophylla.
Calcium sulphate 1.69 4.33
Potassium sulphate 11.29 23.62
Potassium chloride 19.90 13.81
Sodium chloride 60.96 58.20
Magnesium chloride 4.35 -
Sodium carbonate 0.53 -
Sodium iodide 1.26 0.12
Total 99.98 99.98

From experiments, it is demonstrated that the extraction is practically complete after four macerations.

The sodium carbonate extract is evaporated, and the residue (the algin, combined with soda) when dry resembles gum in appearance, but can be obtained in thin transparent flexible sheets. The solution is slightly alkaline; any great excess of sodium carbonate apparently destroys the algin, whilst excess of acid gelatinizes it so that a solution of only 2 per cent. become semi-solid when acidified. A solution can be neutralized without the algin being precipitated. The solution gives the following reactions with various reagents. Dilute mineral acids generally coagulate it. Boracic acid, however, has no effect; and it is not affected by acetic, formic, citric, tartaric, or benzoic acids. Barium, calcium, strontium, copper, zinc, aluminium, tin, antimony, cobalt, and nickel salts all precipitate it. Ferric chloride gives a dark brown coagulum; mercurous nitrate forms a white precipitate, but mercuric chloride and silver nitrate have no effect. Both basic and normal lead acetates give white precipitates. It is unaffected by magnesium salts; by potassium silicate, dichromate, ferrocyanide, and permanganate; and by sodium borate, tungstate, stannate and succinate, and by tannin. Concentrated sulphuric acid dissolves it; concentrated nitric oxidizes it, oxalic acid being amongst the products. From these reactions it will be seen that it differs from all similar substances: thus, from albumin, by not being coagulated when heated, and by not precipitating silver nitrate; from gelose, by being soluble in dilute alkalis, but insoluble in boiling water, gelose is just the reverse; from gelatin, by giving no reaction with tannin; from starch, by not reacting with iodine; from dextrin, etc., by being insoluble in dilute alcohol and dilute mineral acids. The purest form of algin is the precipitate produced by a mineral acid. It dries to a hard horny substance.

The composition of this substance is still obscure, for although the compounds with calcium, aluminium, barium, and lead have been investigated, no uniform results have been obtained. The sodium carbonate appears to be unaltered in its compound with algin; the carbonic acid is, however, only given off by treating with excess of hydrochloric acid, and beating. When a solution of algin is precipitated by acid, redissolved in alkali, and this treatment repeated, decomposition seems to go on continually. The author then suggests various uses for algin, founded on the properties above described; mixed with starch it could be used as a stiffener for fabrics, or alone as a dressing material, or as a mordant. It would also form a useful food. It can be used to prevent boiler incrustations, for fining wines and spirits, for insulating electrical appliances, etc. It can also be used to replace horn for the manufacture of various moulded articles.—Jour. Chem. Soc., 1883, p. 943; Chem. News, xlvii, p, 254 and 267.

The American Journal of Pharmacy, Vol. 55, 1883, was edited by John M. Maisch.