28 



MILK AND DAIRY PRODUCTS PART 



connection between the bottle and the test-tube can be closed 

 by a plug made from a rubber cork and a long piece of iron 

 wire. The test-tube is also modified, being drawn out into a 

 narrow prolongation at the bottom, which admits of an estima- 

 tion of the amount of dirt being quickly made. The figure 

 below gives a view of this piece of apparatus, which, however, 

 has one drawback in that the bottles only hold half a litre, 

 which is too little if a reliable figure is to be obtained for 

 the amount of dirt present. 



An apparatus which may perhaps supplant those described 

 above is due to Spath, and, as will be seen in Fig. 8, the sedi- 



B 



FIG. 7. Gerber's Apparatus for Estimating Dirt in Milk. 



mentation takes place in a conical vessel or funnel which holds 

 1 litre of milk. The dirt collects in a cavity made in the glass 

 tap at the bottom of the funnel, so that when all has settled it 

 is only necessary to turn the tap and pour the milk out of the 

 funnel. After careful washing of the funnel, the tap is turned 

 again to its original position, distilled water poured in, and the 

 dirt again allowed to settle. When this operation has been 

 repeated several times the contents of the cavity are washed 

 out on to a weighed filter, and the residue treated with alcohol, 

 ether, &c., as mentioned previously. 



It is absolutely essential that no sharp projections or crevices 

 should be present in any of the pieces of apparatus mentioned 



