266 QUEENSLAND AGRICULTURAL JOURNAL. [1 Sgpr., 1899. 
The next bottle may consist of an ordinary Winchester quart—which, 
by-the-by, holds half-a- gallon, for what reason one is unable to say; but itis safe to 
assume thatdown in that neighbourhood they are not so liberal as to sell spirituous 
liquids by the above measure. The burette, or measuring tube, itself is held by 
an ordinary wooden clamp. It is now particular to notice the position of the 
elass tubing, which is most important. Virstly, where the air enters it goes 
right into the soda solution. The other tubing must not touch the solution in 
the Winchester quart bottle. The next lot of tubing, however, must go right 
to the bottom of the solution, which it is to conduct to and fill the burette with. 
Clearly notice this: The first bottle does not supply anything to the burette, 
but absorbs the water and carbonic acid of the air, al would alter the known 
strength of solution in the Winchester quart bottle. The carbonic acid tends 
to turn the caustic soda into carbonate, thus using up the strong alkaline 
properties of the former. Perhaps it would be best to add that the small bottle 
of soda solution, after doing its work for some considerable period, gets used up 
and becomes acid, and therefore not performing its necessary functions. It is 
therefore advisable to always colour it with a little phenol-pthalein, which gives 
it a strong pink tinge, and tells you at once to renew the soda when that colour 
disappears. 
The two bottles containing the solutions it is essential should be placed on 
some shelf above the burette, so that the syphon principle can act easily. To 
fill the burette, all that is necessary ix to squeeze the spring cock B. To those 
desirous of obtaining this apparatus, and not inclined to take the trouble of 
constructing it themselves, it can be bought ready for fitting up at one firm of 
chemical apparatus maker's. i 
PERFORMING THE TEST. 
Fill up the burette to the 0 mark, takine out, of course, the indiarubber 
cork, and replacing when not usin e¢the soda. Now, the soda is of such a strength 
that 1 cubic centimetre is capable of neutralising exactly ‘01 (100th) of a gramme 
of lactic acid. i 
A burette, it may be well to know, is usually graduated into 10 or 20 parts, 
as the case may be, each of which is again divided into ten divisions, small 
truly, but easily discernible. 
Our liquid to be tested—such as cream, milk, whey, &¢.—is now brought 
upon the scene, and a pipette capable of measuring out 10 ce. is used. It is 
best always to rinse out the pipette with the liquid you are about to test, whieh 
gives greater accuracy. After measuring out the 10 cc. (a mark on the pipette 
denoting how full it should be), it is put in a small white porcelain basin. 
Phenol-pthalein, an indicator derived from coal-tar and dissolved in alcohol, 
is next added to the 10 ce. milk or cream, two or three drops being sufficient. 
This phenol-pthalein, kept in a dropping-bottle for convenience, has the properties 
of turning pink in an alkaline solution, but remains colourless in the presence 
of acid. It is the most valuable of indicators for this purpose, as others fail 
to answer as well. 
The dish with milk is now put underneath the burette, and by pressing 
spring cock A the caustic soda runs in very gently—best in drops. ‘The liquid 
up to this time is colourless, but when a certain amount of the soda solution has 
been run init turns slightly pink. The more added, the deeper the colour. 
Stop as soon as the faintest trace of pink appears, and read off the burette how 
much soda has been used to neutralise the acidity in the milk. Suppose two 
large and one small divisions haye been used, then, as 10 cc. of milk have been 
taken, each ce. on the burette is equal to “1 per cent. of lactic acid, or the two 
large and one small divisions indicate -21 per cent. acid (reckoned all as lactic), 
or the percentage which would be present in ordinary cheese-making milk. 
If ten whole divisions were used, then it would indicate 1 per cent. acid, or 
the amount likely to be found in a starter of sour whey. In dropping the soda 
into the solution when testing, it should be stirred all the time with a piece of 
glass rod to ensure proper mixing taking place. 
