An investigation on calcium (II) oxalate as solubility and universal standard.

The investigation on calcium (II) oxalate is carried out in order to study its solubility in different ionic media. In the same conditions the protonation constants of oxalate and the stability of complex species have been determined. As the stoichiometric composition of the solid calcium (II) oxalate prepared for the investigation was accurately checked, the salt CaC2O4 x H2O is proposed as universal (chelometry, redox, acidimetry) standard. Results of titrations support this possibility.

Taurocholate and taurodeoxycholate: gel formation and protonation constants.

Taurocholate (TC) and taurodeoxycholate (TDC) in aqueous solutions, in the presence of sodium and hydrogen ions can give micellar products, even differently protonated. This phenomenon is investigated in this paper to explain whether the assumption of hydrogen ions is to attribute to the micellar aggregates, or to the protonation of taurocholate and taurodeoxycholate, respectively. In the course of this research, often the formation of gel occurred immediately after the mixture of the reagents (sodium, hydrogen ions and anions of bile acids) or after some time, depending on the concentrations of the reagents. No author mentions this evidence, but experiments carried out in the presence of gel are not reproducible because the investigated solutions cannot be considered in real equilibrium. The protonation study was performed by means of electromotive force measurements of a galvanic cell involving a glass electrode, at 25 degrees C and 1.00 mol dm(-3) NaCl, as ionic medium. The obtained protonation constants had the following values: log k1 = 0.07+/- 0.02 for TC and log k'1 = 1.60 +/- 0.03 for TDC.

Ratios between content of fatty acids as markers for mixture of cow and goat milk.

The fat of mixture of goat and cow milk, extracted by di-ethylic ether, was gas chromatographically analysed in order to propose an analytical procedure suitable to reveal small additions of cow milk to goat milk. The obtained results show evident differences in the percentages of some fatty acids. An attempt to apply the peak area ratios, corresponding to the methyl esters of fatty acids, suggested by the literature for cow milk did not yield good results. Other ratios suitable to reveal even the presence of low percentages (up to 5 %) of cow milk in goat milk were found and proposed in this paper. Such ratios are sensitive and can be defined markers towards cow or goat milk and also towards extraneous fat like lard or colza seeds oil.