298 ASH. [CH. XV 



Hellriegel. La7idw. Vers.-stat iv. (1862). 

 Stood. Landw. Vers.-stat xxxvi. (1889). 

 Kraus (abstr.). Bot Gentralhlatt XLix. (1892). 

 Lesage. Compt rend. cxii. (1891). 

 LoEW. Biol. Gentralhlatt xi. (1891). 



Flora. 1892. 

 SCHIMPER. Flora. 1890. 



Inorganic salts. Ash of tissues. 



The relations of various inorganic salts to metabolism 

 are studied by culture experiments or by examining the 

 ash of various tissues. The method of culture experiments 

 is described in Part I., p. 58. 



The best processes for obtaining the ash of a tissue are 

 fully discussed in Fresenius, Quantitative Analysis, Special 

 part, sixth English edition, pp. 678 — 690, and full details 

 for determining the constituents are given. 



Studies on the ash of tissues are only useful for 

 determining the distribution of bases and of chlorine and 

 silica; the other acid radicles commonly present, viz. CO2, 

 SO3, P2O5, do not represent the proportions in which they 

 were present as such in the original tissue, indeed in 

 extreme cases they may have been entirely formed during 

 incineration; but estimations of P2O5 may sometimes be 

 useful, since if much P2O5 is found, the greater part of it 

 was probably present as such originally. 



In the case of readily fusible ash the practice commonly 

 followed in the preparation of ash of sugars is very useful, 

 viz. sulphating, but the chlorine will be expelled and cannot 

 be estimated in a sulphated ash. 



