Cryoscopic experiments

Consistent with this, the F nmr spectra of solutions at 0° showed the presence of HSO3F, and separate cryoscopic experiments with pure H2SO4 as the sole solute gave a value of u close to unity. 

In some cases, simultaneously with the quenching of the normal fluorescence a new structureless emission band appeals at about 6000 cm-1 to the red side of the monomer fluorescence spectrum (Figure 6.4). This phenomenon was first observed in pyrene solution by Forster and was explained as due to transitory complex formation between the ground and the excited state molecules since the absorption spectrum was not modified by increase in concentration. Furthermore, cryoscopic experiments gave negative results for the presence of ground state dimers. These shortlived excited state dimers are called pxcimers to differentiate them from... 

C NMR spectroscopy shows the C2 resonance at < 13C 165.1 and Cl resonance at 128.3. As expected with the formation of dication 210, (Z)-/3-nitrostyrene 211 gives the identical spectra from CF3SO3H. Cryoscopic experiments also confirmed the formation of the dicationic species in the superacid. 

At ordinary temperature, sodium perchlorate crystallizes as the very deliquescent monohydrate, but above 50° C. as the anhydrous salt.2 Its deliquescent character hinders its technical application. The melting-point 3 of the anhydrous salt is 482° C. On heating, it is decomposed into chloride and oxygen, a proportion of chlorate being simultaneously formed.4 From cryoscopic experiments with sodium sulphate as solvent, Lowenherz6 inferred the molecular formula to be NaCIO. ... 

Association degree (n) is defined as n = Cnominai/Cexp where Cnominai is the concentration of the lithium species in the solution referred to the monomer and Ce p the concentration calculated from cryoscopic experiments. 

There is an equilibrium between the dimer and monomer, and molecular orbital study suggests that the heterochiral dimer is more stable than the homochiral isomer. The existence and behavior of the dimeric species were well confirmed by experiments such as cryoscopic molecular weight and NMR measurement. In the NMR study of a DAIB-catalyzed dialkylzinc addition reaction, noticeable changes were observed in the spectrum of the homochiral dimer on the addition of benzaldehyde, while the spectrum of the heterochiral complex remained the same. This may imply that the heterochiral complex is very stable and does not react, and the homochiral dimer leads to the reaction product. 

The apparatus used in this experiment is shown in Fig. 1. The thermometer is either a special cryoscopic mercury thermometer of appropriate range, with graduations every 0.01 or 0.02°C, a resistance thermometer with a resolution of 0.01°C, or a calibrated thermistor. In this experiment an aqueous solution of a weak or strong acid is mixed with crushed ice until equilibrium is attained. The temperature is recorded, and two or more aliquots of the liquid phase are withdrawn for titration to determine the equilibrium nominal concentration iiiq. The ice to be used should preferably be distilled-water ice. 

In highly acidic and oxidizing solutions like fluorosulfuric, sulfuric, and disulfuric acids with additional oxidants like selenium dioxide, peroxydisulfuryl difluoride or SbFs, Sc4 + salts can be prepared (see equations 1-3). The products have been characterized by cryoscopic, conductometric, and spectroscopic experiments. ... 

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