THE ASH OF PLANTS. 209 



of the fixed ingredients. In the clover leaf, at a time 

 when it was totally destitute of sulphates, there existed 

 an amount of sulphur which, in the form of sulphuric 

 oxide, would have made 13.7% of the fixed ingredients, 

 or one per cent of the dry leaf itself.* 



Other ash-ingredients. — Salm-Horstmarhas describ- 

 ed some experiments, from which he infers that a minute 

 amount of Lithium and Fluorine (bhe latter as fluoride 

 of potassium) are indispensable to the fruiting of barley. 

 {Jour, far prakt. Chem., 84. p. 140.) The same observer, 

 some years ago, was led to conclude that a trace of Titan- 

 ium is a necessary ingredient of plants. The later re- 

 sults of water-culture would appear to demonstrate that 

 these conclusions are erroneous. 



The rare alkali-metal, Rubidium, has been found in the 

 sugar-beet, in tobacco, coffee, tea, and the grape. It doubt- 

 less occurs, perhaps together with the similar Caesium in 

 many other plants, though always in very minute quan- 

 tity. Bii-ner and Lucanus found that these bodies, in the 

 absence of potassium, acted as poisons to the oat. ( Vs. 

 St., VIII, p. 147.) 



According to Nobbe, Schroeder and Erdmann, Lith- 

 ium is very injurious to buckwheat, even in presence of 

 potassium. When lithium was subsbituted for two- 

 thirds of the potiissium of a normal nutritive solution, 

 buckwheat vegetated indeed for 3 months, the stem 

 reaching a length of 18 inches, but the plant was small 

 and unhealthy, the leaves were pale and the older ones 

 dropped away, as shown by VIII, plate I; {Vs. St., 

 XIII, p. 356). 



*Arendt was the first to estimate sulphuric oxide (SOj) in vegetable 

 matters with accuracy, and to discriminate it from the sulphur of or- 

 ganic- compounds. This chemist separated the sulphates of the oat- 

 plant by extracting the pulverized material with acidulated water. He 

 likewise estimated the total sulphiir by a special method, and by sub- 

 tracting the sulphur of the sulphuric oxide from the total he obtained as 

 a difference that portion of sulphur which belonged to the albuminoids, 

 etc. In his analysis of clover, UlbrioM followed a similar plan. (Vs. St., 

 Ill, p. 147.) As has already been stated, many of the older analyses are 

 wholly untrustworthy as regards sulphur ajia sulphuric oxide. 



M 



