1 6 MICRO-CHEMICAL REAGENTS. 



MINERAL ACIDS. 1 



SULPHURIC ACID (Oil of Vitriol). 



Sulphuric acid is used in a concentrated or dilute 

 form according to circumstances. The most use- 

 ful proportion is obtained by diluting one volume 

 of strong acid with three of water. 2 



Dilute sulphuric acid causes starch grains to 

 swell, and similarly affects cellulose, especially in 

 collenchyma, at the same time transforming it 

 into one of its isomers, amyloid, which differs from 

 cellulose in assuming a blue color when treated 

 with iodine. Hence, to determine whether a cell- 

 wall consists of pure cellulose, it is only necessary 

 to treat it first with a tincture of iodine and then 

 with sulphuric acid, 3 when it turns blue, if unin- 

 crusted. 



Concentrated sulphuric acid dissolves both cell- 

 wall and starch grains, greatly swelling all parts it 



1 In using any of these acids a large cover-glass should be employed to 

 prevent injury to the objective. 



2 Dippel: Das Mikroskop, I., p. 276. Nageli: Das Mikroskop, 1877, 

 p. 474. Weiss: Allgem. Bot., 1878, I., p. 62, etc. Hofmeister : Hand- 

 buch, I., p. 252, etc. 



3 [M. Vetillart advises the use of the following mixture, in place of pure 

 acid, in the cellulose test. Three volumes of sulphuric acid (spec. grav. 

 1.84), one of water, and two of glycerine, are slowly mixed to avoid heat- 

 ing. This does not destroy the tissue. Christy's Fibres, p. 17. w. T.] 



