16 BULLETIN 600, U. S. DEPARTMENT OF AGRICULTURE. 
plant, lettuce, and tobacco plant, where the potash and lime are 
abnormally high, the sum of the sulphur and chlorine is also high. 
Vernadsky+ has shown that rubidium and caesium are widely dis- 
tributed in feldspar and micas and consequently in soils. He is of 
the opinion that these alkalies may occur in sufficient quantities in 
agricultural products to affect the accuracy of potassium determina- 
tions. In so far as plants are concerned, the contention of Vernad- 
sky does not seem to be well founded, for there were only three cases 
where the quantity of rubidium was large enough to be detected in 
the potassium determinations, and in those cases the amount of po- 
tassium would be increased by about 0.01 per cent. 
The aluminum in plants varies widely. In some cases there is more 
aluminum than iron. It is true that a large number of errors ac- 
cumulated upon this determination, but every precaution was taken 
to correct for impurities, and it is believed that the results are not 
consistently too high. Unavoidable contamination by soil would, of 
course, result in a figure for aluminum higher than the true one. 
Such contamination would be shown by a correspondingly high silica 
content. High results for aluminum were checked by another an- 
alyst. 
The results with reference to the rarer elements may be sum- 
marized as follows: | 
1. Lithium was found in spectroscopic quantities in all plants ex- 
amined. Rubidium was present in the majority of cases and in 
larger quantities than the other rare alkalies. In cases where the 
amount of Rb,O in the plant equaled or exceeded 0.01 per cent, rare 
alkali minerals are known to occur in the soil on which the plant 
was grown. Caesium was found in the ash of timothy from Mount 
Mica, Paris, Me., the red raspberry from Beryl Mountain, Acworth, 
N. H., and the beets from Marlboro, N. H. Caesium beryls are 
known to occur in the first two localities. 
2. Chromium was occasionally found, though always in very small 
amounts. Vanadium was detected in only six instances and like- 
wise in traces. Molybdenum was not found by delicate chemical 
tests in the ash of any plant. 
3. Barium was found in determinable quantities in the ash of all 
plants examined. Strontium was found in all samples except bean 
seeds. 
4. Titanium was present in the ash of all plants, though in very 
small amounts. With two exceptions, all plants analyzed contained 
aluminum. The percentages of aluminum in peas, beans, one sample 
of alfalfa, pine needles, wheat, and tomato plants are high. The 
peas, beans, and alfalfa were contaminated by soil to which the high 
1 Ueber die Begleiter des Kaliums. 
