The kinetics of the olefin-bromine reaction has been studied in acetic acid solution using three related aliphatic monobasic acids. The course of the reaction clearly indicates a chain mechanism. It is found that the reaction is of the first order with respect to the olefin and the influence of the catalyst hydrogen bromide is pronounced, the experimental evidence favouring a complex formation between olefin and catalyst.

The dark reaction, catalysed and uncatalysed, between methyl substituted acrylic acids and bromine has been investigated at 25°C., 35°C., 42°C., and 50°C. in glacial acetic acid solution. An analysis of the critical increment shows not only group influence but also an orientation effect.

When present in sufficient amounts, different catalysts have been shown to influence the addition of bromine to dimethylacrylic acid in varying degrees. No negative catalysts have been found so far.

A numerical estimation of the angles between wave-normal and vibration direction of the elastic waves for various classes of crystal has been given. The anisotropy in elastic wave propagation is strikingly manifested by the crystal Ammonium di-hydrogen phosphate belonging to the tetragonal system, which shows a maximum inclination of thirty-four degrees. Numerical studies have also been carried out for this crystal to obtain an estimate of the deviation of the ray vector from the direction of the wavenormal.