ADDITION OF ANTISEPTICS 67 



sodium hydroxide followed by boiling. Distinct red 

 color shows the presence of formalin. 



4. Deniges recommends the fuchsin method: To 40 

 c.c. of a 0.5 per cent, solution of fuchsin are added 250 

 c.c. of water, 10 c.c. of a solution of sodium bisulphite 

 and 100 c.c. pure sulphuric acid. Upon standing, the 

 liquid becomes decolorized. To 10 c.c. of the milk under 

 examination is added 1 c.c. of the prepared decolorized 

 fuchsin solution ; after 5 to 6 minutes at the most, if for- 

 maldehyde be present, an intense carmine red appears, 

 which becomes violet blue upon the addition of 2 c.c. 

 hydrochloric acid. 



[5. Richmond has modified and simplified Hehners' 

 test so that it is most convenient in milk inspection. It 

 is made as follows : To a small quantity of milk, in a 

 test tube, add an equal quantity of water. Pour a little 

 90 per cent, commercial sulphuric acid down the wall of 

 the tube so that it will form a layer at the bottom. If 

 formaldehyde be present, a bluish or violet zone devel- 

 ops at the junction of the acid and milk. If no formal- 

 dehyde be present, a faint, slightly greenish ring forms. 

 This test is effective even when so little formaldehyde is 

 present as 1 part in 200,000. 



6. Leffmann 10 recommends the following test, as one 

 of the most delicate and positive : " To a few c.c. of the 

 suspected liquid, a pinch of phenylhydrazin hydrochlo- 

 ride is added, the liquid shaken and a drop of a dilute 

 solution of sodium nitroprusside added and then a few 

 drops of sodium hydroxide. Milk containing formalde- 

 hyde gives a grayish green. If the test is applied to the 

 pure solution obtained by distilling the sample a char- 

 acteristic deep blue is produced. " 



In distilling milk to obtain a distillate containing f or- 



10 Analysis of Milk and Milk Products. 



