768 
TABLE II. 
Composition of solution. Resistance. | Decrease in resistance. 
5 cc. CaCl, 6 aq. | 8.709 X 2000 c. Ohm ey 
5 ce. CaCl»6 aq. +0.005 cc. NayC,O, 8.452 < 2000c.Ohm | 0.257 >< 2000 c. Ohm 
5 cc. CaCl, 6 ag.t0.010 cc.Na,C,0, 8.200 >< 2000c.Ohm | 0.252 2000 c. Ohm 
5 cc. CaCl, 6 aq. +0.015 cc. Na;C,0,| 7.929 2000 c. Ohm | 0.271 > 2000 c. Ohm 
5 cc. Calls 6 ag.t0.020 cc.NagC,0,, 7.696 & 2000c.Ohm | 0.233 2000 c. Ohm 
5 cc. CaCl, 6 aq.+-0.025 cc. Na,C,0,) 7.600 * 2000c.Ohm | 0.096 2000 c. Ohm 
see. CaCl, 6 aq.+0.030 cc. Na,C,0, 7.500 X 2000c.Ohm | 0.100 > 2000 c. Ohm 
5 cc. CaCl. 6 ag.+0.035 ce. NajC,0, 7.410 > 2000 c. Ohm | 0.090 2000 c. Ohm 
Subsequently more determinations of a similar kind were made 
by us, which always gave a result of 0.053—0.58, — a mean of 
0.055 — for the solubility product. 
Here it must be remarked still that it cannot be expected that 
the solubility product will just have been reached at the end of an 
addition; the mean value, therefore, has to be taken. 
There is still the possibility that the decrease in resistance came 
about because the oxalate added in such large quantities did 
practically not dissociate completely; the way in which the decrease 
would take place then would not be such a sudden one. To control 
this the same quantities of oxalate were added to 5 c.c. of distilled 
water; the conductivity kept increasing proportionally to the quan- 
tities added. 
We have now found by two methods which are independent of 
each other the constant value of 0.055 m.m. for the solubility 
product, when Ca” and C,O," ions are added together. 
The solubility of CaC,O0, has been found by Konurauscn to be 
4.35. 10 5 Mol per L. (18°); the solubility product calculated from 
this is 0.0019 m.m. per L. and this is much below the value found 
by us. 5 
Konrrauscn measured the conductivity of a saturated solution of 
CaC,O0,; he therefore did not start out from the individual ions. 
Herz u. Mens!) found by adding together the ions a value of 
0.034 gram per L. for the.solubility of CaC,O, from which follows 
1) Ber. 36. 4, p. 3717. 
1 
