32 PROVISIONAL METHODS FOB ANALYSIS OF FOODS. 



Remove the inner beaker, weigh into it 50 grams of fat, and note the temperature 

 carefully. Then, from a pipette which will deliver it in approximately one minute, 

 add 10 cc of the strongest sulphuric acid a which is at the same temperature as the oil. 



While the acid is being introduced, stir the oil and acid with an accurate ther- 

 mometer. Then hold the thermometer bulb carefully in the center of the mixture, 

 and when the mercury reaches the highest point note the reading. It is easy to 

 determine this point as the column of mercury remains stationary for some time. It 

 is necessary to take care not to read the temperature too soon, as some oils take con- 

 siderable time to reach their maximum point. 



The difference between the initial reading and the final reading, expressed in 

 degrees centigrade, gives the Maumene number. 



Great care must be taken to have the acid of the highest strength. With the semi- 

 drying oils, such as cotton-seed, the use of this strength of acid will cause foaming 

 and make it almost impossible to obtain the correct rise of temperature. With such 

 oils, either a weaker acid will have to be used and the results compared with the rise 

 of temperature with water, or a dilution with paraffin oil made. It is always best to 

 test the apparatus and acid by use of water and oils of known purity. With 50 

 grams of water and 10 cc of 99 per cent sulphuric acid, Thomson and Ballantyne b 

 obtained a rise of 46.5 C. Working with acid of specific gravity of 1.844, the average 

 of a number of determinations in this laboratory was 45, but this will vary with the 

 apparatus and manipulator. 



The acid which is used in testing the apparatus should be used in all the determi- 

 nations and care should be taken that it does not lose its strength. When this test 

 is conducted with care, it is one of the most valuable in detection of adulteration in 

 fats and oils. 



In reporting results obtained, the rise of temperature with water should be stated, 

 otherwise no comparative value can be attached to the results. 



15. DETERMINATION OF RESIN OIL. 



Take the pure oil or a definite dilution with petroleum ether and polarize in a 

 200 mm tube. 



Resin oil has a polarization of from +30 to +40 on the sugar scale (Schmidt and 

 Haensch) in a 200 mm tube while other oils read between 1+ and 1. 



16. HALPHEN* REACTION FOR COTTON-SEED OIL. 



Carbon disulphid, containing about 1 per cent of sulphur in solution, is mixed 

 with an equal volume of amyl alcohol. Mix equal volumes of this reagent and the 

 oil under examination and heat in a bath of boiling brine for fifteen minutes. In 

 the presence of as little as 1 per cent of cotton-seed oil, an orange or red color is 

 produced, which is characteristic. 



Lard and lard oil from animals fed on cotton-seed meal will give a faint reaction; 

 also the fatty acids. 



This test is more sensitive than the Bechi test and less liable to give unsatisfactory 

 results in the hands of an inexperienced person. It is not affected by rancidity. 

 The depth of color is proportional, to a certain extent, to the amount of oil present, 

 and by making comparative tests with cotton-seed oil some idea as to the amount pres- 

 ent can be obtained, but it must be remembered that different oils react with dif- 

 ferent intensities, and oils which have been heated to 200 to 210 C. d react with greatly 



a See appendix, p. 151. 

 Jour. Soc. Chem. Ind., 1891, 10, 234. 



=G. Halphen, Jour. Pharm. China., 1897, 6, 390-391. Analyst, 1897, 22, 326. Allen, Com. Org. Anal., 

 3d ed., vol. 2, pt. 1, p. 143. Winton, Conn., Exp. Sta. Kept., 1900, pt. 2, p. 144. 

 d Allen, Com. Org. Anal., 3 ed., vol. 2, pt. 1, p. 143. 



