182 Prof. H. Rose on the Inorganic Constituents 



leaves an ash having the form of the plant, which, as in the 

 preceding instances, is not destroyed after exhaustion with 

 water and muriatic acid, whicli removes some lime. Its com- 

 position was then as follows : — 



Silica . . . 94-66 

 Alumina . . 1*77 

 Lime . . . 2*99 



99'4.2 



It is very probable that the substance stated to be alumina 

 in these analyses is really phosphate of lime or magnesia. 

 Alumina has not hitherto been detected with certainty in the 

 ash of plants. 



Appendix VI. and VII. 



Examination of the Ash of Wheat and Wheat-straw. 

 By m. Weber. 



The quantity of substance used amounted to SOO grms. in 

 the case of the grain, and 100 grms. in that of the straw. 



Aqueous extract. — During evaporation it deposited copious 

 films of silica. That of the grain left a residue weighing 1*4 13 

 grm., that of the straw r216 grm. ; it had the following 

 composition : — 



Chloride of potassium 

 Chloride of sodium 

 Potash .... 



Soda 



Sulphuric acid 

 Phosphoric acid . 

 Silica 



98-78 99-92 



The presence of so large a quantity of silica in the aqueous 

 extract of the straw is very remarkable. A soluble compound 

 of chloride of potassium and silica must be formed under cer- 

 tain circumstances. The films of silica deposited during eva- 

 poration, were not changed by digestion with muriatic acid ; 

 nor did they exhibit any regular structure under the micro- 

 scope, but consisted of pure silica. 



Potash and soda exist in the aqueous extract of the car- 

 bonized wheat in combination with phosphoric acid in the 

 form of Z»-phosphates. The amount of phosphoric acid re- 

 quired by calculation is 32-72 per cent. 



