-----------+---------- _Chemical Examination._ _b. Water, Total Solids, and Ash._--Five grammes of the fresh milk are weighed in a tared platinum dish, having a flat bottom, which is placed on a water-bath, where it is allowed to remain for about three hours. It is then transferred to a water-oven, and the dish is subsequently weighed, from time to time, until the weight becomes constant. The loss in weight is the _water_ present; the difference between the weight of the platinum capsule and its weight with the remaining contents gives the amount of _total solids_, which, in milk of good quality, should not be under 12 per cent. The inorganic salts (ash) can now be determined by carefully incinerating the residual contents of the capsule. Too high a temperature is to be avoided in this process, in order to prevent the fusion of the ash, which should, however, be ignited until it shows a greyish-white colour. The amount of ash in genuine milk ranges from 0·70 to 0·80 per cent. The addition of water naturally decreases this proportion as well as that of the total milk-solids. _c. Fat, Milk Solids not Fat, Caseine, and Milk Sugar._--An approximate estimation of the fat in milk was formerly made by the use of the _creamometer_. This instrument consists simply of a long glass tube, provided at its upper end with a scale. The milk under examination is introduced into the tube and allowed to remain at rest for about 24 hours, or until the stratum of cream has completely collected upon its surface; the quantity is then read off by means of the attached scale. The results afforded by the creamometer are, however, far from reliable. Cream is really milk rich in fat, caseine, etc., and the quantitative relation it bears to the true amount of fat present is not always a direct one. A recent form of _lactoscope_, devised by Feser, is less objectionable, and is in very general use for the rapid estimation of fat in milk. It consists essentially of a glass cylinder, provided with two scales, one being graduated into c.c., the other, into percentages of fat. In the lower end of the instrument is a contraction, in which is placed a cylindrical piece of white glass, graduated with well-defined black lines. In using the lactoscope, 4 c.c. of the milk are introduced into the instrument by means of a pipette, and water is gradually added, with shaking, until the black marks on the small white cylinder become just visible. Upon now referring to the c.c. scale, the quantity of water used to effect the necessary dilution is ascertained, and the corresponding percentage of fat in the sample is indicated by the percentage scale.[22]