60 MARKET DAIRYING 
Most of the sampling is done by either of two 
methods: (1) by means of a half ounce dipper, shown 
in Fig. 21, or (2) by means of long narrow tubes, one 
of which is shown in Fig. 22. 
The dipper furnishes a simple and easy means of 
sampling milk. Where the milk is thoroughly mixed, 
and the variations in quantity from day to day are 
‘slight, the dipper method of sampling is accurate. 
The other method of sampling is illustrated by the 
Scovell sampler (Fig. 23). The main tube of the sampler 
is open at both ends, the lower of which closely fits into 
a cap provided with three elliptical openings. As the 
sampler is lowered into the milk the latter rushes through 
the openings filling the tube to the height of the milk in 
the can. When the cap strikes the bottom of the can 
the tube slides over the openings, thus permitting the 
sample to be withdrawn and emptied into the composite 
jar. 
This sampler has the advantage of always taking an 
aliquot portion of the milk, and furnishing an accurate 
sample when the sampling is somewhat delayed, because 
it takes as much milk from the top as it does from the 
bottom of the can. 
The McKay sampler (see page 66) works on the 
same principle as the Scovell and has proven very 
satisfactory. 
Preservatives. Milk cannot be satisfactorily tested 
after it has loppered owing to the difficulty of securing 
an accurate sample. This makes it necessary to add some 
preservative to the composite samples to keep them sweet. 
The best preservatives for this purpose are corrosive 
sublimate, formalin, and bichromate of potash. All of 
these are poisons and care must be taken to place them 
