Material.Rise of
 temperature
with bromin.		 Iodin No. Calculated
Iodin No.
Butter fat6.637.136.3
Olive oil15.080.882.5
Maize ”21.5122.0118.2
Cotton ”19.4107.1106.7
Castor ”15.083.882.5
Linseed oil30.4160.7167.2
Codliver ”28.0144.0140.0

327. Modification of the Heat of Bromination Method.—The method described above by Hehner and Mitchell presents many grave difficulties in manipulation, on account of the inconvenience of handling liquid bromin. The process is made practicable by dissolving both the oil or fat and the bromin in chloroform, or better in carbon tetrachlorid, in which condition the bromin solution is easily handled by means of a special pipette.[289]

In order to make a number of analyses of the same sample ten grams of the fat may be dissolved in chloroform or carbon tetrachlorid and the volume completed with the same solvent to fifty cubic centimeters. In like manner twenty cubic centimeters of the bromin are dissolved in one of the solvents named and the volume completed to 100 cubic centimeters therewith.

For convenience of manipulation the solutions are thus made of such a strength that five cubic centimeters of each represent one gram of the fat and one cubic centimeter of the liquid bromin respectively.

Fig. 99. Apparatus for Determining Heat of Bromination.

The apparatus used for the work is shown in the accompanying [figure]. The pipette for handling the bromin solution is so arranged as to be filled by the pressure of a rubber bulb, thus avoiding the danger of sucking the bromin vapor into the mouth. The filling is secured by keeping the bromin solution in a heavy erlenmeyer with a side tubulure such as is used for filtering under pressure. The solutions are mixed in a long tube, held in a larger vessel, from which the air is exhausted to secure a minimum radiation of heat. A delicate thermometer graduated in tenths serves to register the rise of temperature. The fat solution is first placed in the test tube, with care not to pour it down the sides of the tube but to add it by means of a pipette reaching nearly to the bottom. The whole apparatus having been allowed to come to a standard temperature the bromin solution is allowed to run in quickly from the pipette. No stirring is required as the liquids are sufficiently mixed by the addition of the bromin solution. The mercury in the thermometer rapidly rises and is read at its maximum point by means of a magnifying glass. With a thermometer graduated in tenths, it is easy to read to twentieths of a degree.

It is evident that the rise of temperature obtained depends on similar conditions to those mentioned in connection with sulfuric saponification. Each system of apparatus must be carefully calibrated under standard conditions and when this is done the comparative rise of temperature obtained with various oils and fats will prove of great analytical use. It is evident that the ratio of this rise of temperature to the iodin number must be determined for every system of apparatus and for every method of manipulation employed, and no fixed factor can be given that will apply in every case.

With the apparatus above described and with the method of manipulation given the following data were obtained for the oils mentioned:

Rise of
temperature.
Olive oil20°.5
Refined cottonseed oil  25°.7
Sunflowerseed oil28°.4
Calycanthusseed oil29°.0