NOTES
1328
Vol. 63
Equation 20 indicates that the values of and B” COMPLEXES OF BICARBONATE WITH may be obtained from the intercept and the initial MAGNESIUM AND CALCIUM slope of a plot of l/(Mw)app vs. CO. The value of X BY ISIDOR GREENWALD may differ slightly for each experiment. In that New ] ’ o h University College of Medicine, New Y o l k , N . Y . case the mean value of X for different Comay be subReceived December 11, 1968 stituted for X in equation 21, because under the circumstances considered A2J!lz2/12is a correction term. In their paper Halla and Van Tassel1 made two Due to the same reason M , in equation 21 may be serious errors. They overlooked the fact that my replaced by 1.5 MI,,,provided the actual value for it conclusioii that such complexes existed was based is not available. The factor 1.5 is based on the as- not only upon the results of titrations but also on sumption that the weight distributions of molecular the determination of the solubility of CaC03 in weight in polymeric systems are often ell approxi- the presence, and absence, of NaHC03. Moremated by the “most probable” distribution curve. they made no attempt to ascertain whether It is shown that for this distribution of molecular over, or not such complexes could have been detected weight the term of order X4 neglected in the paren- under their conditions and by their method. theses of equation 21 becomes X4Mz4/270. Thus it If the solubility of COz is not appreciably afis seen that equation 21 may be correct to within fected by the presence of such small quantities of 3%, provided that experiments are performed un- Mg++ or of Ca++, [total C02] in their experiments der such a condition that XM,
