October t, 1884.] 



THE TROPICAL AGRICULTURIST, 



3 '3 



ON THE ECONOMIC APPLICATIONS OF SEAWEED. 



BY EDWARD C. C. STANFORD, F.C.S. 



In 1 802, twenty-two years ago, I had the honour of read- 

 ing a paper before the Society of Arts, on this subject, in this 

 room. The Council marked their appreciation of that paper 

 by awarding me a silver medal, and I cannot forget that the 

 honours of that year were shared by another chemist, my 

 friend, Dr. Grace Calvert, once so well known here, but who 

 has since passed away. When, therefore, I was again invited 

 a little while ago to read a second paper, I felt that some 

 apology was due for riot returning to report progress before. 

 I am bound to admit that, like some wanderers through 

 space, the period has been long and the orbit eccentri ■. 

 For the former, I must plead the difficulty of the sub- 

 ject; for the latter I must remind you that any one 

 who follows seaweed must go to the wildest and most 

 inaccessible shores. 



It is extremely interesting to me, and I trust it may 

 be made somewhat entertaining to you, to look back 

 on that paper, with the light of over twenty years' ex- 

 perience, and see how far the views then put forward 

 were right, and how far they were wrong, premising that 

 even failures are excellent lessons. " Many things have 

 happened since then," and new and better sources have 

 been discovered of many of the products then brought 

 forward for the first time. As however, it may be ad- 

 visable to follow the lines of that paper, I shall first 

 briefly allude to the uses of seaweed for food and for 

 manure, and then speak more at length on the import- 

 ant application of these in the manufacture of kelp, and 

 the production of iodine. 



SEAWEED AS FOOD. 



In this country, little advance has been made in the 

 use of the alga? as food. The alga? generally contain im- 

 portant nitrogenous constituents, and form nutritious art- 

 icles of diet, but they have not been popular. We all 

 like a " sniff of the briny," but we do not cultivate a taste for 

 the internal consumption of our marine vegetables. We 

 are equally guilty, however, in rejecting the majority of 

 the fungi, so largely consumed as an important article of 

 food on the Continent. The alga? are closely allied to 

 these, but have the advantage of containing, as far as is 

 known, no poisonous species. The alga? also contain a 

 large proportion of salts which, however, are easily re- 

 moved, if desirable. 



Ulva latissiihdj or green laver, and Porphyra laciniata, 

 or pink laver, are occasionally used in soups. Rhodo- 

 m&iicb palmata, or dulse, is still sold in the streets of Edin- 

 burgh and Glasgow. Aliara escvlenta, or murlins, is also 

 eaten in Ireland; some others are occasionally used, but, 

 as a general food, the alga? are almost unknown. The 

 sweetest species is the Laminaria saccharine, which is 

 usually covered, when dry, with an efflorescence of man- 

 nitc ; a large quantity of this plant yielded me 7'47 per 

 cent of mannite. It appears to be a product of ferment- 

 ation, and does not exist in the fresh plant. This plant 

 is found only on sandy or gravelly shores. 



The best known British species of the edible alga? is 

 the Ckondrus crispjis, or Irish moss ; this grows far down 

 on the rocks, and is only uncovered at low spring tides. 

 It is obtained mostly from the west coast of Ireland, and 

 after being bleached by exposure to sun and rain, is 

 largely exported to this country and to Germany. It is 

 a gelatinous species, containing a principle known as car- 

 ragheenin; it yielded me 63*7 per cent of this substance. 



The only other gelatinous British species is the Gelid- 

 rum corneitm ; this is not very common, but it furnishes 

 the import known as Japanese isinglass, of which it con- 

 tains 50 per cent. This substance, known also as gelose, 

 was first imported into France, from China, in 1856 ; it 

 has great gelatinising power, much higher than any other 

 material. It is not nitrogenous, and contains carbon 42'S, 

 hydrogen 58, oxygen 51*4. 



The following table shows the value of these species in 

 making jelly. The menting point of the jelly is also ap- 

 pended. 



1,000 parts of water require of — 



Propor- Melting 

 Parts. tion. point. 



Gelose I 1 00° Fahr. 



Oelideum comeum.. 8 2 90° „ 



40 



Propor- Melting 

 Parts. tion. point. 



Irish moss (CTo«-) 



Ill-US LTlSpUS) J 



Isinglass 32 8 70° „ 



Gelatine 32 8 00° „ 



Carragheenin :. 36 U 70° „ 



Agar-agar (Eu- ) m 



cnemia spinosa ) 

 It will be seen that gelose has eight times the gelatinis- 

 ing power of isinglass and gelatine ; but the melting point 

 of the jelly is too high to melt quickly in the mouth] 

 hence gelatine is still the favourite. 



The carragheenin has evidently become altered by evapor- 

 ation. Gelose jelly keeps well, the others soon ;get mouldy 

 Although not fit for jelly, gelose may be valuable in the 

 arts as a substitute for gelatine, which it so much exceeds 

 in gelatinising power. I would specially suggest its use 

 as a substitute for gelatine in the production of instantane- 

 ous photographs. 



The Euchemia spinosa., or agar agar, is an Australian 

 alga, and another important gelatinous species. The algte 

 form a large article of food consumption in China and 

 Japan ; some years ago I procured some of these samples, 

 one was a dark green frond, and the other two were 

 cut up from it, about the size of vermicelli; I append 

 the analyses of three and of a sample of our own laminaria 

 from Loch Eport in North Uist. 



EDIBLE SEAWEEDS. — .JAPAN. 



No. I. — "This is a good average sample, worth to-day, 

 in this market, 11 taels, which at 6s. 6d.. the average 

 value of the tael is 71s. 6d. per pieul of 133 lb.; therefore 

 one ton (16'75 piculs) would cost, in Shanghai, £57 4s. It 

 can be cut finer, and then the price, if it is of the deep green 

 which this is when it leaves me, would be about 14 taels per 

 picul,or£72 10s. per ton." — Extract from letters. 



The sample is green and evenly cut about as fine as ver- 

 micelli. 



No. II. — "Tbis is the worst sample I can find, worth 2 

 taels, which is i-'ll 8s. per ton. The uncut leaf would be 

 more valuable than this if of the colour of No. I. It would 

 fetch £16 per ton." — Extract from same Utters. 



This sample looks like the former deteriorated. 



No. III. — This was apparently the uncut weed. It much 

 resembles in colour and appearance No. IV. 



No. IV. — Laminaria, cut in Loch Eport, North Uist; 

 colour, dark green. Quotations by Mr. Frazer, Yokohama, 

 September 18, 1868:— Fine cut, £17 0s. 8d. ; fine brown, 

 £15 10s. 9d.; large green. £9 14s. 2d— per ton. Specimens 

 of No. IV. were sent out to Yokohama, but they did not 

 take the market. It is remarkable that so high a price 

 as 72s. 6d. per cwt. (or nearly Sri. per lb.) should be realised 

 there for this seaweed for dietetic purposes. 



The taste for marine vegetables must be acquired, but 

 those who have eaten them often are said to become very 

 fond of them; and I have known some gentlemen in the 

 Highlands, no mean pi.lges of diet ; who consider a dish 



