558 Bnller .— Contributions to our Knowledge of the 
In comparing the effect of the stimulus given by different 
substances, one at once notices the somewhat striking fact 
that compounds containing the negative radicle of malic acid 
attract much more strongly than any other tested. In each 
table is to be found a substance with the acid radicle in 
question. In Table I it will be noticed that whereas the 
malate attracts strongly at the concentration 1-0V0 mol, 
TABLE II. Isotonic coejf. — 4. 
Standard solutions of 
Potassium nitrate 
J in parts of a mol 
) in grains per cent . 
1 
10.1 
tV 
i-oi 
TO 
O-I 
TTRRT 
O-OI 
TO 0 0 0 
O-OOI 
TUT (ITT 
0-0001 
Sodium malate 
Na 2 C 4 H 4 0 5 
178.12 
N 
A 
A 
A 
a 
O 
Potassium tartrate 
KARA 
226*2 
N 
A 
a 
0 
0 
° 
Sodium tartrate 
Na 2 C 4 HA 
194.1 
N 
A 
a 
0 
0 
O 
Sodium-potass, tartrate 
KNaQHA 
210.2 
N 
A 
a 
0 
0 
O 
Potassium oxalate 
k 2 c 2 o 4 
166-2 
N 
A 
a 
0 
0 
O 
Potassium phosphate 
* k 2 hpo 4 
174.2 
N 
A 
a 
0 
0 
O 
Sodium phosphate 
Na 2 HP 0 4 
142 
N 
A 
a 
0 
0 
O 
Ammonium phosphate 
Am 2 HP 0 4 
132 
N 
A 
a 
0 
0 
O 
Potassium sulphate 
k 2 so 4 
174.2 
N 
A 
a 
0 
0 
O 
Sodium sulphate 
Na 2 S 0 4 
142 
N 
A 
a? 
0 
0 
0 
Ammonium sulphate 
Am 2 S 0 4 
132 
N 
A 
a 
0 
0 
0 
Caesium sulphate 
Cs 2 S 0 4 
362 
N 
A 
0 
0 
° 
0 
Sodium sulphite 
Na 2 S 0 3 
126 
N 
A i 
a 
0 
0 
0 
Sodium thiosulphate 
Na 2 S 2 0 3 
158 
N 
A 
a ? 
0 
0 
0 
Calcium nitrate 
Ca(N 0 3 ) 2 
164 
N 
0 
0 
0 
0 
0 
Calcium chloride 
CaCl 2 
110-9 
N 
0 
0 
0 ! 
0 
0 
Potassium carbonate 
k 2 co 3 
138.2 
N 
N | 
0? 
0 ! 
0 
0 
and also, although very weakly 1 , at the other salts at 
these concentrations do not give an observable reaction. 
A similar statement is true of Table II, and also of Table III 
if maleic acid be excepted. Maleic acid, however, only gives 
a very weak attraction at a concentration isomolecular with 
1 Compare Pfeffer, loc. cit., Bd. i, p. 379, and Voegler, Bot. Zeit., 1891, No. 40, 
p. 659. 
