258 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
phuric acid to make a paste is added to the ash and 8 
c.c. of methy] alcohol is mixed with it. The vapor which 
is then given off is ignited. If boric acid or borax is 
present, even in very small quantity, the flame wiil be 
green. 
Turmeric Test—Add 6 or 7 drops of hydrochloric 
acid to 10 c.c. of milk and, after coagulation has occurred, 
filter. Dip a piece of turmeric paper into the filtrate and 
allow it to dry. If boric acid is present in the proportion 
of 0.02 per cent. or borax in the proportion of 0.03 per 
cent., the paper will be colored cherry-red (Kuhl) ; this 
color will be changed to bluish-black by ammonia water. 
Another method of applying the turmeric test is de- 
scribed by Farrington and Woll as follows: “ One hun- 
dred cubic centimetres of milk are made alkaline with 
a soda or potash solution and then evaporated to dryness 
and incinerated. The ash is dissolved in water, to which 
a little hydrochloric acid has been added, and the solu- 
tion filtered. A strip of turmeric paper moistened with 
the filtrate will be colored reddish-brown when dried at 
100° C. on a watch glass if boric acid is present.” 
Formaldehyde.— Formaldehyde, the favorite preserva- 
tive for milk, is used in the form of formaldehyde solution, 
formalin, formol, etc. A very small quantity (0.008 per 
cent. of formaldehyde, 0.02 per cent. of formalin) will 
prevent curdling for four days. The following tests may 
be used for detecting the presence of formaldehyde: 
Richmond’s Test.—Place a small quantity of milk 
in a test tube, add an equal quantity of water and then 
pour a little commercial sulphuric acid slowly down the 
side of the tube so that it will form a layer at the bottom. 
A bluish or violet ring at the point where the acid and 
milk come in contact indicates the presence of formalde- 
hyde. If no formaldehyde is present a faint, greenish 
