SOME CONTRIBUTIONS TO PLANT-CnEMISTRY. 



71 



SOME CONTEIBUTIONS TO PLINT-CHEMISTRY. 



By a. H. Chuech, 



{^Continued from vol. iv., p. 172.) 



7. Lactuca sativa. On submitting some well-grown plants of Cab- 

 bage-lettuce to analysis, in order to gain some insight into their 

 chemical composition and dietetic value, the" following observations 

 were made. The leaves lost, as might have been predicted, an im- 

 mense amount of water when dried, first in warm air, and then at 100° 

 C. The dry plant, when burnt in order to obtain its ash, deflagrated 

 owing to the abundance of nitrates present. On this account it was 

 necessary to adopt a special method of ascertaining the amount of 

 albuminoid matter which this plant contains. This was accomplished 

 by determining the nitrogen in a portion of the dried plant which had 

 been treated with a hot solution of carbolic acid. This solution re- 

 moves other nitrogenous matters, such as nitrates and ammonia salts, 

 but it leaves in an insoluble and coagulated state such nitrogenous 

 matters as are truly albuminoid in their nature. Thus analysed, fresh 

 Lettuces were found to contain, in 100 parts : 



Water . . . . .95-98 



Albuminoids 

 Starch, Sugar, Gum 

 Cellulose and Lignose 

 Chlorophyll and Fat 

 Ash 



•71 

 1-68 

 •52 

 •22 

 •89 



100^00 



8. Chondrus crispus. Many conflicting statements have been 

 published as to the occurrence of sulphur-compounds in " Irish Moss." 

 The analyses recently made in my laboratory do not show the nature 

 of the compounds in which the sulphur is contained, but they prove 

 that this element occurs in Chondrus crispus in large proportion, and 

 only in part as sulphates. Some of this seaweed which had been 

 carefully picked over and ground to powder was oxidised in the wet- 

 way by means of nitric acid and potassium chlorate ; and then the 

 sulphuric acid thus formed was converted into barium sulphate in the 

 usual manner. By this plan it was ascertained that Chondrus crispus, 

 in its usual state of moisture as it occurs in commerce, contains no 

 less than 6"41 per cent, of sulphur, although the amount retained in 

 its ash is but 2*64 per. cent. 100 parts of the air-dry plant, freed 

 from impurities by mechanical means, gave the following results on 

 analysis : 



Water . . . . . 18^78 



Albuminoids 

 Mucilage, &c. 

 Cellulose 

 Ash 



9^38 

 55^54 



3-15 

 14-15 



100-00 



