687 
sulphuric acid, concentrated hydrochloric acid containing a little 
phenol, concentrated nitric acid and bromine water, and she com- 
pletely dried the preparations over sulphuric acid in a dessicator. 
She maintains that with sulphuric acid and hydrochloric acid con- 
taining phenol, this is absolutely necessary and is to be recommended 
in the case of nitric acid and of bromine water. Tammes says that 
when the preparations are even slightly moist, the reaction sometimes 
does not take place, and she attributes this, especially in the case of 
sulphuric acid, to the presence of traces of water. When investigating 
the crystals which have been separated out in tbe cells and tissues 
as also when working with plants and parts of plants, which have 
not yet been treated with other reagents, Tammes prescribes the 
careful drying of the preparations. Konr *) completely agrees with 
this. My impression is, however, that he does not support his opinion 
by experiments. G. and F. Tosrer *) state moreover that the assertion 
that the reaction with sulphuric acid succeeds only with anhydrous 
objects, is not correct. 
With respect to Tammes’ method of procedure it must be remarked 
that a thorough drying is not a suitable method for obtaining beau- 
tiful preparations, and there is no theoretical explanation why this 
drying is necessary, for concentrated nitric acid contains 50 °/, water, 
concentrated hydrochloric acid 75°/, and bromine water being a 
saturated solution of bromine in water contains nearly 97 °/, water, 
whilst concentrated sulphuric acid also always contains a certain 
percentage of water, 4-6. Only when concentrated sulpburic acid 
is used can I imagine that the smail quantities of water in the 
preparations can be of influence, but in this case a much simpler 
means can be used than the thorough drying of the preparations, 
namely, the use of fuming sulphuric acid, so that the water with 
which it eomes into contact is converted into sulphuric acid 
(H, 5,0, + H,O = 2H, SO). Thus fuming sulphuric acid has a 
stronger action than the concentrated acid. 
The assertion that traces of water can interfere with the reaction, 
is wholly incorrect, as I shall further prove. On the contrary the 
best results are obtained with somewhat diluted sulphuric acid. By 
mixing concentrated sulphuric acid of 95°/, with 10, 20, 30, 40 
and 50°/, water, I obtained dilute sulphuric acid of 85'/,, 76, 66'/,, 
}) F. G. Kout, Untersuchungen über das Carotin und seine physiol. Bedeutung 
in der Pflanze, 1902, p. 44. 
*) G. und F. Tosier, Untersuchungen über Natur und Auftreten von Carotinen, 
II]. Zur Bildung des Lycopins und über Beziehungen zwischen Farb- und Speicher- 
stoffen bei Daucus, Ber. d. d. bot. Ges. 30. Jahrg. Heft I, 1912, p. 33. 
