METAMORPHOSED FUCOID SCHISTS IN SCANDINAVIA. 157 



the magnesia precipitated by phosphate of soda and an excess of ammonia 

 From the alkaline solution, which besides potash and soda contained an excess 

 of barytes, the barytes was precipitated by carbonate of ammonia; there was 

 afterwards added muriate of ammonia until the potash and soda were changed 

 into chlorides, upon which the whole was evaporated and heated, for the pur- 

 pose of expelling the excess of muriate of ammonia, and then the whole was 

 weighed. In order to ascertain the quantity of potash, the salt was dissolved 

 and evaporated with an excess of chloride of platinum, the dried mass dissolved 

 in alcohol of about 40 per cent., and from the weight of the chloride of potas- 

 sium and platinum, the weight of the chloride of potassium, and thus that of 

 the potash, was calculated. 



In most cases the weight of the soda was found by calculation from the 

 weight of the chloride of sodium, which again was ascertained, by deducting 

 the weight of the chloride of potassium from the total weight of the alkaline 

 chlorides. In some instances, the quantity of chloride of sodium was deter- 

 mined, by mixing the alcoholic solution of chloride of sodium and chloride of 

 platinum with sulphuret of ammonia ; in order to precipitate all the platinum, 

 evaporating the liquid to dryness, dissolving the salt in water, passing the 

 solution through a filter, and after having evaporated it to dryness, heating 

 it to expel the muriate of ammonia, upon which the pure chloride of sodium 

 remained. In some cases the quantity of chlorium in the ashes was ascertained 

 by nitrate of silver. 



The portion of the ashes which was insoluble in water was dissolved in 

 muriatic acid, which left the sand undissolved upon which the solution was 

 diluted, and precipitated by ammonia. This precipitate is mentioned in the 

 tabular view as phosphate of lime, which composed the greater part of it ; 

 though it contained, in many instances, some alumina and the oxides of iron 

 and manganese. The presence of phosphoric acid was ascertained by dissolving 

 the precipitate in muriatic acid, adding alcohol and sulphuric acid, by which 

 sulphate of lime was precipitated ; the remaining alcoholic solution was mixed 

 with an excess of ammonia, upon which an alkaline solution of chloride of 

 magnesia and muriate of ammonia precipitated ammonio-phosphate of mag- 

 nesium. 



The ashes of all the plants of the Fucus tribe which I have analysed con- 

 tain phosphate of lime. The lime and magnesia which had been in the in- 

 soluble part of the ashes was separated in the usual way. The following 

 tabular view gives the constituent parts of the ashes of the different fucoidal 

 plants which I have analysed. The carbonic acid of the ashes combined with 

 lime is not stated. With regard to the silica, it is mentioned in some in- 

 stances as sand, which of course had been mechanically adhering to the 

 plant, in other instances it was in a state which made it probable, that it be- 

 longed to the constitution of the plant, which however is not quite proved. 

 The great quantity of oxide of manganese, I may observe, in the ashes of 

 Padina pavonia, is curious and doubtful; because I have not yet had an op- 

 portunity of repeating my analysis satisfactorily to determine this point. 



