365 
this interchange of the two can lead appears for instance in the 
wellknown tables of LANDOLT-BORNSTEIN de Aufl. 1912. There we 
read in connection with d-galactose: ‘“Anfangsdrehung nach 7 Minuten 
als « Modifikation + 117°.5; Enddrehung nach 7 Stunden als 8-Modi- 
fication + 80°.27.” In fact the final rotation which an ordinary 
d-galactose solution exhibits is 80°.27 or simply 81°. But this is not 
the rotation of the second modification; that rotation is + 53°. A 
~ 
rotation of 81° results when the two modifications of 117°5 and 
+ 53° are in equilibrium. And this equilibrium comes about when 
we start out from 8 as well as when we do from a. In both cases 
a mixture results with a rotatory power of 81°. 
It is perhaps useful that what has been brought forward for d-galactose should 
also be applied to d-glucose, which is so much more used. 
Tanner distinguishes 3 forms of glucose: an « form with [~],}, = 106°, a @ form 
with [7]; =53° and a y form with [#],)=19°; Both z and 2 forms when 
dissolved in water finally exhibit a rotation of 53°. The @ form of Tanrer, 
according to the researches of Roux and others, must be considered as an 
equilibrium between x and 7, and this is at present generally accepted too. @ is 
therefore no independent modification, but merely a mixture. But now we read the 
following: There exist two forms of glucose, — the z and the @ forms and not 
infrequently there is added: The « form is converted into the @ form. How can 
those who maintain that we have to deal with a reversible reaction here, speak 
of an equilibrium between ~ and #? If it were stated that the a form is partially 
converted into the @ form, it would be clear. 
We find the case put differently again by Hotteman in his wellknown text book 
of Organic Chemistry, 5th ed., 1912, p. 300. He also speaks of an z form of 
106°, a 2 form of 19° and a y form of 53°. This y form is according to bim 
a mixture of « and 7. The y of Tanret Hotreman calls thus 7. 
The question arises why ‘Tanrets’ nomenclature was not stuck to. After Emir 
FiscHer had shown us how to prepare artificial glucosides !) it appeared to him that 
stereoisomeric modifications of each glucoside existed. One was acted upon by beer 
ferment (invertine), and the other by emulsine. *) By way of distinction he called the 
first the «-glucoside and the second the (-glucoside and the corresponding forms 
of glucose z and -glucose 4). It is to this nomenclature that later writers seem 
to have stuck. For this there was an inducement to some extent as if there 
existed only two forms it was not quite rational to call the second y. Coincidentally 
that which Em Frscaer calls @ corresponds with what Tanret at the same time 
gave the name of y. 
To explain now the partial retention of the galactose solution 
which is passed through the kidneys, we assume that only one of the 
!) Emmi Fiscuer, Ber. d. D. Chem. Ges. 26, 2400 (1893). 
2?) The same, Ber. 27, 2985, (1894); 28, 1145, (1895). 
3) Cf. also E. Fiscuer, Z. f. physiol. Chemie 26, 60, (1898). 
