Rapid cold stabilization

Rapid Cold Stabilization Static Contact Process... 

There are several rapid cold stabilization processes for precipitating tartrates (static and dynamic contact processes). These techniques have certain economic advantages, but are not easy to implement. They are described elsewhere (Sections 1.7.3 and 1.7.4). 

In practice, a rapid-response test is required for monitoring the effectiveness of artificial cold stabilization. The preceding results show quite clearly that the tests based on induced crystallization are relatively unreliable for predicting the stability of a wine at 0°C. 

It is true that, in contact treatments involving large-scale seeding, the wine s background is less important. Indeed, enologists do not always have this information if the wine has been purchased from another winery. In any event, wine must be well prepared and, above all, properly clarified, to ensure the effectiveness of rapid artificial cold stabilization treatments. 

Substituents in the 3- and 5-positions of 1,2,4-thiadiazoles exert a marked stabilizing effect on the heterocyclic ring towards alkalis and reducing agents. Thus, the parent compound is rapidly decomposed by cold aqueous alkali, whereas 3,5-diphenyl-1,2,4-thiadiazole reacts with alkalis only on prolonged boiling <65AHC(5)ll9>. 

General.—It seems certain that the free acids corresponding to these salts do not exist in the solid state, and that, with the possible exception of hexavanadic acid, mentioned below, they are also incapable of existing in solution, although salts of all the acids are known. The most stable class of salts is the metavanadates, the next in order of stability being the pyrovanadates, while the orthovanadates are few in number and undergo rapid hydrolysis even in the cold, to give the pyro-salts ... 

Hydrolytic and oxidative stability of the cations increase with the base strength of the ligand. Bistrimethylamine-boronium cations are unusually stable. They have been recovered, apparently unchanged after prolonged periods of time at 100°in concentrated acids (HC1, H2SO4, andHNOs) and 10% NaOH. On the other hand bisdialkyl sulfide boronium ions are rapidly attacked by cold water. The ion [BH2(OH2)2]+ is perhaps the most unstable thermally and hydrolytically of the boronium ions reported. Evidence has been claimed for its existence in 8 MHC1 solution at 70° 95,96). 

---