Water of pure

One c.c. of 0.10 per cent, solution in distilled water of pure permanganate of potash, added to 100 c.c. of the acetone, must retain its distinctive colour for not less than 30 minutes. This test should be made at a temperature of 60° F. 

It was also shown by Hinton and Wilson that CeCl3 inhibited the corrosion in soft tap water of pure Zn and of steel electroplated with Zn. 

Prepare the phenol test dilutions from a standardised stock 5 per cent solution in distilled water of pure phenol (crystallising-point not less than 40-5°). Prepare the disinfectant test dilutions (usually in a series differing by 10 per cent or thereabouts) from an initial 1 or 2 per cent master dilution in distilled water. In making the master dilution always measure the disinfectant by pipette into the required volume of water and then mix thoroughly any other procedure might affect the quality of the emulsion formed and hence its disinfecting power. 

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