Solutions in Sulfuric Acid

CeUulose is subsequendy regenerated from the viscose solution in sulfuric acid and carbon disulfide is Hberated. These are the basic steps in manufacturing viscose rayon. The production of regenerated ceUulose is estimated to account for mote than 75% of the total carbon disulfide consumption woddwide... 

Dilute nitric acid or sulfuric acid in place of concentrated fuming nitric acid or oleum (SO3 solution in sulfuric acid)... 

P 43] Typically, a flow rate of 250 pi min was established by use of syringe or peristaltic pumps [70]. A 0.1 M methanol solution in sulfuric acid was used as reaction medium. Reaction was carried out at room temperature at a voltage of 4 V. 

Although substituted benzoic acids give esters when their acylium ion-containing solutions in sulfuric acid are poured into alcohol, the sort of acylium ion that loses carbon monoxide gives an ether instead.254... 

In some cases spectroscopic evidence for such species exists. Thus the ultraviolet spectrum of acetophenone in aqueous sulfuric acid changes markedly as the concentration of acid is increased.278 In concentrated sulfuric acid simple aldehydes and ketones exists completely in the conjugate acid form. Unsaturated ketones give colored solutions in sulfuric acid and have -factors greater than two. The higher i-factors... 

Another method that has proved extremely useful in obtaining information about the nature of solutes in sulfuric acid solution is the measurement of freezing point depressions. The freezing point constant (k) for sulfuric acid is 6.12 kg °C mol-1. For idea) solutions, the depression of the freezing point is given by... 

The colored solutions produced on dissolving elemental selenium in sulfuric acid were first observed by Magnus in 1827 80). Since then a number of workers have investigated the nature of selenium solutions in sulfuric acid, oleum, and sulfur trioxide, providing 81) a substantial amount of data but little understanding of the system. Recently, it has been shown that these solutions contain the yellow Se and green Seg " polyatomic cations 82). 

The material considered in the preceding sections shows that the FB and EB methods can be successfully applied to the solution of these problems providing information not only on the equilibrium but also on the kinetic properties of polymer chains. This is particularly valuable in those cases in which the application of other more common methods is difficult or even impossible (e.g. sedimentation measurements of polymer solutions in sulfuric acid). 

A few measurements of the conductivities of solutions in sulfuric acid were made by the early workers 6,63,61,63) but there were considerable differences between their results and conclusions, again partly because of a lack of understanding of the solvent self-dissociation and the contribution that it made to the conductivities of the solutions studied. A comprehensive investigation of the conductivities of solutions in sulfuric acid was first made by Gillespie and Wasif 45) and this showed that such measurements were of considerable value in the study of the ionizations of solutes in sulfuric acid. 

It may be noted that in solution in sulfuric acid no more than two hydrogen sulfate groups become attached to a silicon atom. In cases where a tri- or tetra(hydrogensulfate) could in principle be formed oxy-sulfato compounds are in fact obtained. 

Evidence for the basicity of the S=0 group is also given by the fact that a number of substituted diphenyl sulfoxides, R2S=0, have been shown to behave as strong bases and the corresponding sulfones, R2S02, as weak bases in solution in sulfuric acid (55) ... 

Sodium dichromate, Na2Cr207, is applied not only in solutions in sulfuric acid but also in solutions in perchloric acid [620, 621], acetic acid [622, 623, 624, 625, 626, 627, 628], benzene, and dimethyl sulfoxide [629], In the presence of tetrabutylammonium bisulfate, dichloromethane, used as a water-insoluble solvent, extracts the product from the aqueous phase (phase transfer) [630]. 

The freezing-point depression constant of pure H2SO4 is 6.12 K kg mol . When 2.3 g of ethanol (C2H5OH) is dissolved in 1.00 kg of pure sulfuric acid, the freezing point of the solution is 0.92 K lower than the freezing point of pure sulfuric acid. Determine how many particles are formed as 1 molecule of ethanol goes into solution in sulfuric acid. 

Literature contains very few reports on ion pair chromatography upon impregnated layers. Schill et al. developed theoretically interesting systems 27-29), which allow the computation of the parameter governing ion pair chromatography. Such a system is described for the separation of certain tertiary and quaternary ammonium compounds8 . The system uses acetylated cellulose as support, 1-butanol or 1-pentanol as stationary phase and aqueous salt solutions in sulfuric acid as mobile phase. The salt solutions, which consist of NaCl or NaBr or NaC104 and sulfuric acid play the part of counter-ions. 

For an excellent discussion of solutions in sulfuric acid see Hammett, Physical Organic Chemistry, McGraw-Hill Book Co., New York, 1943. See also pp. 39, 225 in this book and Newman, Craig, and Garrett, J. Am. Chetn. Soc.9 71, 869 (1949). 

The chemical name for Hypalon is chlorosulfonated polyethylene and it has excellent resistance to heat, ozone and oxidising chemicals and has good abrasion resistance. It can be compounded for outstanding resistance to oxidising chemicals, such as sodium hypochlorite solutions in sulfuric acid saturated with chlorine and concentrated phosphoric acid. It is one of the few synthetic rubbers that can be mixed in any colour without loss in mechanical properties. 

The samples which were cured chemically with acetic anhydride and pyridine, and then heated to remove solvent, appeared to be incompletely imidized, and yielded lower molecular weights than thermally cured samples from the same polyamic acid. In addition, these samples produced a bright red solution in sulfuric acid, in contrast to the orange-gold color observed in solutions from thermally cured samples. The red color disappeared within 24 hours, when the molecular weights were determined. This color was also observed by Wallach (4), who carried out viscosity measurements on sulfuric acid solutions of chemically cured PMDA/DAPE polyimides. Wallach observed a slow decrease in the dilute solution viscosity with time over a period of hours from the initial preparation of the solution. We have not observed any decrease in viscosity for 24 hours for solutions prepared from thermally cured samples. Polyimide samples which have been cured chemically have been shown to contain a small percentage of isoimide, which is then converted to the more stable imide at higher temperatures (8-9). The observed red color in sulfuric acid solutions may be because protonation of... 

The results obtained here confirm their findings, and extend them by showing that even a small percent of N-methylation is sufficient to change the hydrodynamic properties of the para-linked aromatic polyamide molecule. The agreement between the molecular weights measured for polymer 7 (50% N-methyl substitutive) in 96% sulfuric acid and the N-methyl pyrrolidone with 5% LiCl and 1% water implies that this polymer forms a molecularly disperse solution in the latter solvent. This observation differs significantly from the report by Tsvetkov et al. (6) and Koton and Nozova (5) that the fully methylated polymer only formed molecularly disperse solutions in sulfuric acid. 

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