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’ which are not saturated with respect to R, but to L-\- R) and 
this goes on when we increase the temperature, until above t t the salt 
R can absolutely exist no longer in the presence of any solution 
whatever (retardation phenomena excluded). The temperature region 
t % — t t is called the transition interval. 
In my research I have endeavoured to construct experimentally 
a similar diagram for the system strychnine /-tartrate, strychnine 
d-tartrate and water. For this purpose complete isotherms were 
determined successively by observing the change in fhe solubility 
of D, or L, if L or D was previously dissolved in water. In 
this manner I determined in this system the isotherm of 40° which, 
being situated above the transition point found by Ladenborg 
and Doctor, had a form which agrees very well with that of 
the lines LC 1 and DC 1 . Isotherms at a lower temperature were 
then determined in a similar manner. First of all, I determined 
the D- and Z-solubility curves at 25°, 16° and 7.5°, which, 
notwithstanding the fact that these are interrupted by the solubility 
curve of R, could be followed up to their intersecting point. The 
solubility as to L -j- R and D -f- R was then measured at the said 
temperatures (also that of D -j- L, and this always agreed very well 
with the intersecting point of the D- and /,-solubility curves found, 
finally, by extrapolation). 
When the solubility of these two salt couples was known, I placed 
them on the L- and the Z)-axis, connected these points with a straight 
line and looked, in the case of 1 -f- R solutions, for the intersecting 
point with the L solubility curve; on the other hand in the case of 
D R solutions the intersecting point with the D curve was deter¬ 
mined* In this manner, points on the lines PA and PB were deter¬ 
mined successively in an indirect way and it was my ^intention to 
endeavour to trace the intersection of PA with OR, as the terminal 
point of the transition interval would then be known and the analogy 
between partial racemates and the inorganic double salts investigated 
by van ’t Hoff and his scholars be completely demonstrated. 1 
succeeded in showing that at 7.5 C the solubility of the racemate 
must be put down in the point where the L curve of the isotherm 
of that temperature intersects the line OR, and also that R and 
RL became equal as regards solubility. This gave the end of the 
transition interval and this temperature region, which in Ladenbcrg 
and Doctor’s research was supposed not to exist at all, was shown 
to extend over about 20°. Saturated solutions of the partial racemate 
are therefore stable below 7.5° only ; the solubility of the salt may, 
