Drift- Weed Kelp from Orkney. 253 



salts and water, the real amount of soluble salts will be ob- 

 tained, which is as follows : — 



Insoluble Salts. Soluble Salts. Water. 



29-736 63-464 6-8 



Analysis of Insoluble Salts. 



The following is the description of analyses and results 

 obtained from the insoluble salts. 



Testing Analysis of Insoluble Salts. — Before proceeding to 

 the quantitative analysis of the insoluble salts, a qualitative 

 investigation was made. The kelp under examination was 

 very hard, with a strong alkaline taste, and greyish colour, 

 with black portions of carbonaceous matter interspersed 

 through it. It was partly soluble in water. That which re- 

 mained undissolved in water was a greyish powder, which, 

 when ignited, became perfectly white. On addition of acid 

 to the insoluble matter, carbonic acid and sulphuretted hydro- 

 gen were evolved, and the greater part of the salts dissolved, 

 that which remained being silica. The portion thus dissolved 

 in acid gave, on addition of ammonia, a copious precipitate, 

 which proved on examination to be phosphate of lime. To 

 prove the presence of phosphoric acid it was converted into 

 phosphate of iron by Berthier's method, and the phosphoric 

 acid precipitated, as ammonia phosphate of magnesia, the 

 iron being detained by tartaric acid, with a trace of iron. On 

 the phosphate of lime being separated by nitration, the nitrate 

 gave, with oxalate of ammonia, a white pulverulent precipi- 

 tate, proving the presence of lime, which must originally have 

 existed as carbonate or sulphuret. After the oxalate of lime 

 had been removed, phosphate of soda and ammonia produced 

 a white crystalline precipitate, indicating the presence of 

 magnesia. 



Quantitative Analysis of Insoluble Salts. 



Estimation of Organic Matter. — As has been already men- 

 tioned, the specimen of kelp under examination had not been 

 entirely freed from nitrogenous matter. This was discovered 

 while deflagrating a portion of the kelp with nitre, when a 



VOL. LIII. NO. CVI. — OCTOBER 1852. S 



