These determinations must necessarily be only approximate, as the plants were collected by different persons who exercised different degrees of care in freeing them from adherent soil, and possibly in drying the plants, so that the main value of these figures is their aid in determining the amount of barium present. * * * * * FOOTNOTES: [185] The detailed analysis of O'Brine can be found on page 32 of this report. [186] All ash and barium determinations were made from the dried plants save when otherwise specified. [187] Evidently these plants must have been imperfectly freed from soil. =BARIUM DETERMINATIONS IN THE ASH OF LOCO PLANTS.= Attention has been called to the fact that in ashing plants containing barium a part at least of this barium is converted into the insoluble sulphate and a part into the carbonate, so that the characteristic pharmacological action of the ash will depend not upon the total barium present, but upon the form in which it occurs--little action if much BaSO_{4}, and more complete if more BaCO_{3} results. A further difficulty in the recognition of barium in plants is due to the fact that certain inorganic salts interfere with the precipitation by H_{2}SO_{4}. A specimen of _Aragallus lamberti_ (Hugo, summer of 1907) with 12.44 per cent of ash was examined for its barium content by Hillebrand's method.[188] The method was as follows: Two grams of the ash were first fused with sodium carbonate and the fused mass washed with water containing sodium carbonate. The residue was washed into a beaker and treated with a few drops of sulphuric acid. The residue now remaining was filtered and after ignition was treated with hydrofluoric and sulphuric acids. After evaporating off these acids, the residue was treated with sulphuric acid water, filtered, and then fused with sodium carbonate. After extracting with sodium carbonate water, the residue was dissolved in just enough hydrochloric acid and precipitated with sulphuric acid. The precipitate was dissolved in concentrated sulphuric acid and reprecipitated by water and weighed as BaSO_{4}.[189] So far as the writer can ascertain, there have been no control experiments made for this method to determine the experimental error. Of the above ash, 1.998 grams gave 5.2 milligrams of BaSO_{4}, which would correspond to 75.75 milligrams of barium acetate crystals-- Ba(C_{2}H_{3}O_{2})_{2}+H_{2}O--in 200 grams of the dried plant. The residue by the Hillebrand method after weighing was tested with the spectroscope and gave a bright spectrum for barium. The same ash was analyzed by the Bureau of Chemistry, using a shorter method, and they reported 2.7 milligrams of barium sulphate in 1.1217 grams of ash. A second sample collected earlier in the summer, with an ash content of 18.6 per cent, was shown to yield barium corresponding to 3.4 milligrams of BaSO_{4} in 2.5 grams of the ash.[190]