212 Mk. G. W. Brown on Drift Weed Kelp from Orkney. 



Estimaiion 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 removed the 

 previously combined silica, and the sand remained: — 



Sand. 



per cent. 



1-55 

 1-60 

 1-575 



Estiination of Carbonic Acid. — The carbonic acid was determined 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 salts. The gas passing 

 through the barytes solution yielded a precipitate of carbonate of barytes, 

 which was weighed. 



Carb. of Barytes, Carbonic Acid. ^"'"CT^'ent"^'''' 



500 grains gave 10205 ... 22-91 ... 4-58 



Estimation of Sulphur. — The sulphur was determined by means of the 

 same apparatus as was employed for the estimation 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. 

 As O3 + 3 S H = As Ss + 3 H 0. 

 The tersulphuret of arsenic was held in solution by the soda, but when 

 muriatic acid was added the yellow tersulphuret fell. This precipitate 

 was then thrown on a weighed filter, and washed with water slightly 

 acidulated with muriatic acid. 



Tersidpliiuet o . i, SiUpliur, 



of Arsenic. siupnui. percent. 



500 grains gave 5-16 ... 1-932 ... -386 



Estimation of Phosphate of Lime. — The insoluble salts having been 

 dissolved in acid, and the silica separated, the phosphate of lime was 

 precipitated by ammonia. 



Pliospliatc of Phospliate of Lime, 



Lime. per cent 



400 grains gave 4284 1071 



.500 " « 52-50 10-50 



500 " " 52-30 10-46 



Mean 10556 



Estimaiion of Alumina. — To ascertain if the phosphate of lime contained 

 alumina, it was dissolved in acid, and then boiled in an excess of strong 

 caustic soda, which would redissolve any alumina. It was found that it 

 contained a small quantity, which wa.s probably accidentally introduced 

 by tho nau.stic soda or other rcagenlp. 



