104 ESTIMATION OF TOTAL SOLIDS AND ASH. 



the mouth ; it is advisable to throw away this first quantity 

 The milk is again sucked up, the finger placed over the end 

 of the pipette, and the milk allowed to run down to the mark, 

 care being taken that air bubbles are not included in the portion 

 measured. The pipette is held over dish No. 1 and the finger 

 removed ; the milk runs into the dish, and the drop adhering 

 to the end is removed by touching it against the side of the 

 dish ; the last drops must not be removed by blowing. Mean- 

 while the assistant has closed can No. 1 and stirred can No. 2, 

 from which 5 grammes are measured in a similar manner, without, 

 however, washing out the pipette ; this is transferred to dish 

 No. 2, and the whole of the samples are taken similarly. 



The next step is to enter the designation of the samples and 

 the number of the dish into which each has been placed in a 

 book provided for that purpose ; the tray containing the dishes 

 is then conveyed to the water-bath. The water-bath should be 

 of copper, about 6 inches deep, and provided with a lid containing 

 a suitable number of holes in which the dishes can rest ; the 

 number of these will vary with the number of samples to be 

 examined daily ; it is convenient to have a projecting collar 

 about a quarter of an inch deep round each hole, as this facili- 

 tates the putting on and removal of the dishes, and each should 

 be provided with a lid. If steam is laid on, the bath should be 

 heated by means of a coil laid in the bottom, through which the 

 steam circulates ; the exit of this coil should be connected with 

 a condenser, and the condensed steam serves to supply the 

 laboratory with distilled water. If steam be not laid on, the 

 bath must be supported on an iron support at such height as to 

 allow of a burner being placed underneath ; in either case an 

 arrangement for keeping the water level constant in the bath is 

 necessary. 



After the dishes have been for about half an hour on the bath, 

 provided it has been boiling briskly, it will be noticed that a 

 distended skin has formed on the surface of the milk ; this must 

 be broken with a needle mounted in a handle, care being exer- 

 cised that no portion of the skin is brought away on the needle. 

 The object of this is to prevent the milk drying in flakes, which 

 may be blown away by draughts, and the estimation lost. Should 

 the dishes be forgotten, or should any other reason prevent 

 the stirring being done at the proper moment, a few drops of 

 water may be added to the milk residue, which will have the 

 effect of making the flakes settle down and adhere to the dish. 

 When the dishes have been on the water-bath for three hours, 

 they should be taken off, placed on a tray having two or three 

 thicknesses of blotting-paper on the bottom to remove adhering 

 drops of water, and transferred to a water-oven or air-bath. 



