828 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
When the discussion was finished, the President appointed Professors 
Ewell, Seaman, and Claypole, Mr. Tolman, and Dr. Stillson as a com- 
mittee to map out the work of a standing committee on this branch of 
microscopy. 
Millon’s Reagent.* — Signor A. Poli calls attention to the unsatis- 
factory quality of this reagent as obtained from some of the leading 
manufacturers, its property of imparting a rose-colour to proteids being 
often only very feebly displayed. He believes this to arise from the fact 
that it is not a stable compound, and it should therefore always be pre- 
pared fresh by the operator himself. Millon’s prescription for preparing 
the reagent is as follows : — Mercury is dissolved in an equal weight of 
nitric acid diluted by 4*5 equivalents of water. The solution is com- 
menced in the cold, and finished by heating slightly until all the 
mercury is dissolved. Crystals are then formed, and the liquid is decanted 
and diluted with two volumes of water. The solution thus obtained 
contains mercurous nitrate Hg 2 (N0 3 ) 2 , mercuric nitrate Hg(N0 3 ) 2 , 
and free nitric acid, and is thus a mercurous-mercuric nitrate. In 
consequence of the difficulty of obtaining nitric acid perfectly free from 
water, Signor Poli prefers Poulsen’s method, as follows : — 10 grm. of 
mercury are dissolved in 25 grm. of nitric acid of sp. gr. 1 • 185, heating 
not above 50° C. ; this solution is then mixed with another obtained by 
dissolving 10 grm. of mercury in 22 grm. of nitric acid of sp. gr. 1*25- 
1*30; the reagent should be prepared and employed as much as possible 
in the cold. 
Tests for Mineral Acids and Mineral Bases in Plants.f— Herr A. 
F. W. Schimper recommends the following microchemical tests for 
detecting the presence of mineral acids and mineral bases in the ash of 
plants : — 
Lime. — The production of crystals of calcium sulphate by addition 
of sulphuric acid ; also, in certain cases, the formation of crystals of 
calcium oxalate by addition of ammonium oxalate, or of calcium car- 
bonate by ammonium carbonate. 
Chlorine. — Precipitation by silver nitrate or thallium sulphate. 
Where present in large quantities, potassium or sodium chloride may 
be crystallized out of an aqueous solution of the ash. 
Potassium. — The production of potassium-platinum chloride, in- 
soluble in water and alcohol. 
Magnesium. — The formation of ammonium-magnesium phosphate 
by addition of sodium phosphate or sodium-ammonium phosphate with 
the addition of ammonia. The formation of magnesium-sodium uranate, 
by the use of uranacetyl. 
Sodium. — The same as the last. 
Oxalic Acid. — Formation of calcium oxalate. 
Phosphoric Acid. — The production of ammonium-phospho-molybdate 
by the addition of ammonium molybdate and nitric acid. Formation of 
magnesium-ammonium phosphate. 
Nitric Acid. — Formation of an anilin-blue with diphenylamin. An 
extraordinarily delicate reaction. Production of calcium nitrate. 
* Nuov. Giom. Bot. Ital., xxn. (1890) pp. 446-50. 
f Flora, lxxiii. (1890) pp. 210-20. 
