Potassium occurrence

Tartaric acid is noteworthy for a) the excellent way in which the majority of its salts Crystallise, and h) the frequent occurrence of salts having mixed cations. Examples of the latter are sodium potassium tartrate (or Rochelle salt), C4H40 NaK, used for the preparation of Fehling s solution (p. 525), sodium ammonium tartrate, C4H OaNaNH4, used by Pasteur for his early optical resolution experiments, and potassium antimonyl tartrate (or Tartar Emetic), C4H404K(Sb0). The latter is prepared by boiling a solution of potassium hydrogen tartrate (or cream of tartar ) with antimony trioxide,... 

In determining the values of Ka use is made of the pronounced shift of the UV-vis absorption spectrum of 2.4 upon coordination to the catalytically active ions as is illustrated in Figure 2.4 ". The occurrence of an isosbestic point can be regarded as an indication that there are only two species in solution that contribute to the absorption spectrum free and coordinated dienophile. The exact method of determination of the equilibrium constants is described extensively in reference 75 and is summarised in the experimental section. Since equilibrium constants and rate constants depend on the ionic strength, from this point onward, all measurements have been performed at constant ionic strength of 2.00 M usir potassium nitrate as background electrolyte . 

I) derived from this by dissociation, or in a mobile equilibrium mixture of both these forms. Dobbie et reproduced the spectra of cotarnine solutions containing varying amounts of potassium hydroxide by using cotarnine chloride and hydrocotamine and by dissolving mixtures of the latter two compounds or by placing the separate solutions of these compounds in the apparatus in series. Thus no evidence could be obtained for the occurrence of the amino-aldehyde (3) postulated by Roser. Steiner, Kitasato, and Skinner came to similar conclusions. The band at 285 m/x in alkaline solutions is not due to an aromatic aldehyde. This band also occurs in the spectrum of hydrocotamine (10a) and in the carbinolamine... 

Polyurelhane, 1214 foam, 1214 kinds of, 1214 stretchable, 1214 Polyyncs. occurrence of, 259 Potassium nitrosodisulfonale,... 

Kuznetsov, Polyakov and Stangrit [317, 318] and on KC1 - NaCl - NaF -K2NbF7 by Kovalev, Ioffe and Datlina [319], all in the concentration range of up to 20-25% mass of K2NbF7. In all cases, maximum electro-conductivity was observed at concentrations of about 5-10% mass of K2NbF7. The peaking of the electro-conductivity is explained by the occurrence of two processes with opposite characters. The increase in electro-conductivity is related to the increase in the concentration of potassium ions [319] and fluorine ions [317, 318], whereas the drop in conductivity results from a decrease in free volume due to an increase in NbF72 ion concentration. 

An explanation not easily distinguishable from the one involving resonance with a carbonium ion structure in the transition state is that the reactive species is an ion pair in equilibrium with the covalent molecule. This is quite likely in a solvent insufficiently polar to cause dissociation of the ion pairs. Examples of second order nucleophilic displacements accelerated by the sort of structural change that would stabilize a carbonium ion are of fairly frequent occurrence. Allyl chloride reacts with potassium iodide in acetone at 50° seventy-nine times as fast as does -butyl chloride.209 Another example is the reaction of 3,4-epoxy-1 -butene with methoxide ion.210... 

When evaporating large amounts of impure ether which has been exposed to the air for a long time, the possibility of the occurrence of a violent explosion at the end of the evaporation, due to the presence of peroxides, must be taken Into account. Such ether has a pungent odour, and liberates iodine from an acid solution of potassium iodide. The peroxides can be destroyed by shaking with a weakly acid solution of ferrous sulphate. 

Alkali feldspars (K.NajAlSijOg) form a continuous solid solution series at high temperatures, but tend to exsolve upon cooling into a potassium-rich phase and a sodium-rich phase, resulting in perthitic intergrowths (2). Sodic plagioclases and potassium-rich feldspars tend to be studied together, in part because of similarities in structure, composition, occurrence, and weatherability (e.g., 1[). 

As we have seen in Section II,A, 6-bromo-4-phenylpyrimidine reacts on treatment with potassium amide in liquid ammonia at -75°C into the corresponding 6-amino compound nearly quantitatively according to the Sn(ANRORC) mechanism (71RTC1239). Extensive investigations have been carried out on the scope and limitations of this mechanism and on the several factors that influence the occurrence of the Sn(ANRORC) mechanism in the aminodehalogenation of 4-substituted-6-halogenopyrimidines. 

---