396 TruE AND Gigs: Heavy METALS 
- metals. Mixtures were made in which, in addition to a copper 
salt, salts of sodium, magnesium, calcium and potassium, succes- 
sively, were added. In every case, Ca excepted, the concentra- 
tion in which each compound was present was that which, while 
distinctly retarding growth, still permitted it. We have, there- 
fore, in every case, a salt entering into the combination in a con- | 
centration sufficiently great to be a distinctly toxic agent. The 
- concentrations and other data in this connection appear in Table VI. 
It will be noted in each case that the copper salt permits a_ 
slight growth. When the sodium salt is added, the mixture be- 
TaBLe VI 
ComMpLex MIXTURES OF ONE HEAVY METAL AND AN INCREASING NUMBER OF LIGHTER METALS. 
_ AVERAGE GROWTH-RATES IN MILLIMETERS 
—<———————— 
With common anions | With different anions 
(a) Ay. | (6) | Av. ‘at Av. Beals a |,_ Av. 
Contents of | Growth| Contents of | Growth oan of | Growth Contents of Solu- Growth 
Solutions 24 hrs. | Solutions Sd hrs Solutions 24 hrs tions { 24 Bhs 
= tied | | eee eee ee | ited. | permet ti } - mol 
CuCl, 65536) 5.5 CuCl, | 32768) 1.0 | CuCl, ee 2.5 | Cu(CH,.CO,), | 65536| 8: 
CuCl, | 65536 (CuCl, 32768 CuCl, | 6553 Cu(CHy.CO,), | 65539. 
NaCl 64| 2.5 | NaCl 64| 1.5 | NaCl | Bs 1.0 | Na, 128) 3:0 
— CuCl, | 65536 “CuCl, | 32768 poe |e 6) | Cu(CH,.CO,), | 65536 
5 NaCl 64 NaCl 64 NaCl | 738 | ‘Naso, x 128 
_ MgCl,| 512| 7.0 |MgCl,| 512| 2.5 |MgCl, 1024| 60 | MgCl, 512| 8.0 
CuCl, 65536 “CuCl, | 32768 CuCl, 65536 | Cu(CHy.CO,), | 65536 
6553 u »)2 | 9553) 
NaCl 64 ‘NaCl |” 64 NaCt | "128 Ne SO, 128 
MgCi,| 512 |MgCl,| 512 eC, 1024 | MgCl, 538 
ae 32| 14.5 eae 32| 7.0 |CaCl,| 64] 9.0 | CaCl, 32| 17-0 
CuCl, | 65536 CuCl, | 32768 CuCl, | 65536 Cu(CH,.CO,) 65538 
Mect |< ba NaCl | 64 Nact | 7328 | NesOe a 
MgCl,| 512 MgCl,| 512 Medi, 1024 MgCl, | ee 
CaCl, 3 | CaCl 32 CaCl, 64. CaCl, 34 
KCl 128 | 19.0 Ka 1281 5.5 KCl" 256 10.0  KNO, 128 | 22,0 
Check 13.5 ae 10.5 10,5 | ee? ee ie 
comes somewhat more harmful than the copper salt alone. The 
addition of magnesium to the mixture raises the growth-rate to a 
point beyond that reached in the copper solution, indicating 4 
slightly beneficial antagonistic effect. When to these the calcium 
salt is added, the growth-rate immediately assumes practically 
normal proportions. This neutralizing or antitoxic effect of the 
calcium is very marked. When to the combination just referred 
