THE ASH OF PLANTS. 195 



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 acid, would have 

 made 13.7 | of the fixed ingredients, or one per cent of 

 the dry leaf itself.* 



Other ash-ingredients. Salm-Horstmar has described 

 some experiments, from which he infers that a minute 

 amount of Lithia and Fluorine, (the latter as fluoride of 

 potassium,) are indispensable to the fruiting of barley. 

 (Jour, fur prakt. Chem., 84, p. 140.) The same observer, 

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

 acid is a necessary ingredient of plants. The later results 

 of water-culture would appear to demonstrate that these 

 conclusions are erroneous. 



It is, however, possible, as Mulder has suggested, ( Che- 

 mie der AckerJcrume, II, 341,) that the failure of certain 

 crops, after long-continued cultivation in the same soil, 

 may be due to the exhaustion of some of these less abun- 

 dant and usually overlooked substances. Land not unfre- 

 quently becomes "clover-sick," i. e., refuses to produce 

 good crops of clover, even with the most copious manur- 

 ings. In Yaucluse, according to Mulder, the madder crop 

 has suffered a deterioration in quality the coloring effect 

 of the root having diminished one-fourth as an apparent 

 result of long cultivation on the same soil, although the 

 seed is annually renewed from Asia Minor, and great care 

 is bestowed on its culture. 



The newly discovered element, Rubidium, has been 

 found in the sugar-beet, in tobacco, coffee, tea, and the 



* Arendt was the first to estimate sulphuric acid in vegetable matters with 

 accuracy, and to discriminate it from the sulphur in organic compounds. This 

 chemist determined the sulphuric acid of the oat-plant by extracting the pulver- 

 ized material with acidulated water. He likewise estimated the total sulphur by 

 a special method, and by subtracting the sulphur of the sulphuric acid from the 

 total, he obtained as a difference that portion of sulphur which belonged to the 

 albuminoids, etc. In his analyses of clover, Ulbricht 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 and sulphuric acid. 



