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III. On Sea-Weeds as the sources of Acetic Acid. 

 By John Stenhouse, LL.D., F.R.S.L. ^ E* 



DURING the course of a series of experiments on sea-weeds, 

 an account of which was read before the Roj^al Society 

 on the 18th of April 1850, I had frequently occasion to obseiTe 

 that when a quantity of wet sea-weeds was laid together in a 

 heap in a warm situation for any length of time, it soon began 

 to imdergo a species of fermentation. This, I am aware, is a 

 cu'cumstance which has been not unfrequently observed ; but as 

 no one has hitherto been at the trouble to examine the nature 

 of the acids generated during this fermentation, I was induced 

 to investigate the matter a little more closely. 



At the ordinary temperature of Scotland, even during the 

 summer months, the fermentation of sea-weeds proceeds very 

 slowly, requiring from three to four months for its completion ; 

 but when the weeds are kept at a temperatm-e of from 90° to 

 96° ¥., the process is completed in from two to three weeks. 



I. Six pounds of fresh moist Fucus vesiculosus were put into 

 an earthenware jar along with a little quicklime, and just suffi- 

 cient water to cover them, and were kept for three weeks at the 

 temperature of 96° F. Small quantities of quicklime were added 

 from time to time, so as to keep the mixture slightly alkaline. 

 When the fermentation was completed, the liquid portion, which 

 contained a good deal of mucilage and some acetate of ammonia, 

 was thrown upon a cloth filter, and the clear liquid which passed 

 through was evaporated to diyness and then cautiously heated, 

 so as not to decompose any of the crude acetate of lime, while 

 almost the whole of the mucilaginous matter was rendered inso- 

 luble. The dark brown mass was digested vdth a little water, 

 again filtered, and the clear solution evaporated to di"jaiess. It 

 yielded 4 oz. 2 drams of diy acetate of lime, which was almost 

 entii-ely free from adliering organic matter. When this acetate 

 of lime was distilled with hydi'ochloric acid, it yielded 29 oz. of 

 a pure but feeble vinegar, 1 oz. of which required 24 grs. of 

 anhydrous carbonate of soda to neutralize it. As, therefore, 662 

 grs. of anhydrous carbonate of soda require for saturation 650 

 grs. of anhydrous acetic acid, 1 grain of anhydi'ous carbonate of 

 soda may be regarded as equivalent to 1 gr. of anhydi'ous acetic 

 acid. The 29 oz. of the above-mentioned vinegar, therefore, 

 contained 2i x 1 x 29 = 696 grs. of anhydroi\s acetic acid. As 

 1 pound contains 7000 grs., and 6 pounds of fucus consequently 

 42,000 grs., the 696 grs. of anhydi'ous acetic acid obtained fi'om 

 it give 1-65 per cent, anhydi'ous acetic acid as the produce of the 

 wet sea-weed. 



* Communicated by the Author. 



