Acidity in Milk. 
63 
tnay thus be introduced into the test is, even at its maximum, 
so small that it may be disregarded. The error wJiich may be 
introduced from continuous exposure of the small area of the 
liquid corresponding with the hole at the bottom of the well- 
tube is also so slight that it has no appreciable effect on the 
strength of the solution during any reasonable period, especially 
as this hole is filled by the dropper when the appliance is not 
in use. 
The only other element of the arrangement that has to be 
noticed is the quantity of the liquid to be tested which is taken 
for a sample. For reasons of a technical kind, connected with 
the production of the appliance in a cheap and simple form, 
which it is unnecessary to explain here, the quantity adopted 
for the purpose is three cubic 
centimetres, which gives a 
bulk that is neither too large 
nor too small ; and this quan- 
tity is easily taken from the 
gross bulk of the liquid to 
be tested by means of a glass 
sampling tube, with a rubber 
capsule at one end, and a mark 
on the tube to indicate the 
precise amount to be taken by 
it. 
The general nature of the 
appliances thus described will 
be better understood by refe- 
rence to the accompanying 
wood-cut, which represents 
the bottle of the Neutraliser 
with the dropping-tube rest- 
ing in the well-tube, and on 
either side the dropping-tube 
itself, and the sampling tube. 
A very few words will suffice to explain the proceeding in- 
volved in making the test itself. The end of the sampling-tube 
is inserted in the liquid to be tested, say milk ; the rubber 
capsule is compressed between the finger and thumb, and by 
this means the proper quantity of the milk is taken up in the 
tube, and is then squeezed out into a small glass or cup. In the 
same way a charge of the Neutraliser is taken by means of the 
dropping-tube and dropped into the milk, to which a minute 
quantity of the Indicator has been added, until a permanent 
