. Dairy chemistry: a practical handbook for dairy chemists and others having control of dairies. 166 THE CHEMICAL CONTROL OF THE DAIRY. enough to allow the instrument to float. A cylindrical glass jar (Fig. 6), with foot, is the most suitable vessel for the pur- pose if Soxhlet's lactometer or the thermo lactometer be used ; Vieth's lactometer may be used in a can or tin cup. The lacto- meter is gradually lowered into the milk to the 25th degree, care being taken that the instrument is entirely wetted by the milk and that no air adheres to it. When released, the lactometer will move up and dow
. Dairy chemistry: a practical handbook for dairy chemists and others having control of dairies. 166 THE CHEMICAL CONTROL OF THE DAIRY. enough to allow the instrument to float. A cylindrical glass jar (Fig. 6), with foot, is the most suitable vessel for the pur- pose if Soxhlet's lactometer or the thermo lactometer be used ; Vieth's lactometer may be used in a can or tin cup. The lacto- meter is gradually lowered into the milk to the 25th degree, care being taken that the instrument is entirely wetted by the milk and that no air adheres to it. When released, the lactometer will move up and down, and after a little while become stationary. That degree of the scale which coincides with the surface of the milk is then noted. It will be observed that, where the milk touches the vessel and the stem of the lactometer, the surface is not level, but, in consequence of the adhesion of the milk to the glass, forms a curve. There is no difficulty, however, in ascertaining the exten- Ision of the curve sufficiently near, | 30 '^Si 11 and this has to be allowed for in -==^|| reading off the specific gravity. When using instruments of ordinary size, the curve will be found to extend to about one-half degree. Lactometers indicate the exact specific gravity at a temperature of 60° F. It is, therefore, necessary, as soon as the position of the lactometer has been noted, to remove the instru- ment from the milk, immerse a ther- mometer, and ascertain the tempera- ture. If the temperature is found to be 60° F., the observed specific gravity is correct, but should the temperature of the milk be higher or lower than 00 F., the specific gravity must be corrected by the aid of the Table in the Appendix which is used as follows I Find the temperature of the milk in the uppermost horizontal line, and the observed specific gravity in the tir.^t or lasl vertical column; in the same line with the latter, and under the temperature, is given the corrected specific gravity. For example- Supposi
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