Drift- Weed Kelp from Orkney. 255 



Loss by Ignition. Loss ^ l ^ loU > 



400 grains gave 11-52 2-88 



500 ... 12-18 2.437 



500 ... 1215 3-431 



Mean, 2-582 , u0 £) 



Estimation of Silica and Sand. — A portion of the kelp was 

 weighed out, and the soluble salts washed out with boiling 

 water. When this was accomplished the insoluble salts 

 were dried, and the carbonaceous matter removed by ignition, 

 after which they were dissolved in muriatic acid, which took 

 up the insoluble salts, and left the silica and sand. This 

 residue was then boiled with carbonate of soda, which re- 

 moved the previously combined silica, and the sand remained. 



Silica & Sand. Silica. Sand. Silica, Sand, 



per cent, per cent. 



400 grains gave 13-24 7'01 6-23 1-75 1'55 



400 ... 13-52 7*12 6-40 1-78 1-60 



Mean, 1*765 1-575 



Estimation of Carbonic Acid. — The carbonic acid was deter- 

 mined by introducing the insoluble salts into a flask from 

 which a tube passed into another flask containing barytes 

 water. The carbonic acid was disengaged by the addition of 

 weak muriatic acid to the kelp. The gas passing through 

 the barytes solution yielded a precipitate of carbonate of 

 barytes, which was weighed. >£ hi 



Carbonate of Bar vtes. Carbonic Acid. Carbomc ^ Cld > 



J per cent. 



500 grains gave 102-05 22-91 4-580 



Estimation of Sulphur. — The sulphur was estimated by 

 means of the same apparatus as was employed for the esti- 

 mation of the carbonic acid ; but instead of barytes a solution 

 of arsenious acid in caustic soda was used. When the 

 sulphuretted hydrogen was evolved, by means of muriatic acid, 

 it converted the arsenious acid into the tersulphuret of 

 arsenic. slq.fi ni fioiJifrgc 



As0 3 + 3 SH = AflS^j^O. Hzqizzib 



The tersulphuret of arsenic was held in solution by the 

 soda ; but when muriatic acid was added the yellow tersulphu- 

 ret fell. This precipitate was then thrown on a weighed filter 

 and washed with water slightly acidulated with muriatic acid. 



s2 



