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Unfred States Department of Agriculture, 



BUREAU OF CHEMISTRY. Circular No. 22. 

 WASHWGTOtf, D. C. 



COOPERATIVE WORK ON THE TITER TEST, ASSOCIATION OF OFFI- 

 CIAL AGRICULTURAL CHEMISTS, 1904. 



METHODS INVESTIGATED. 



This important test has been a subject of study in the association for 

 two years. The various modifications of the test in use in this country 

 did not give concordant results, and several of the largest business 

 houses using it expressed a desire that this association should cooper- 

 ate with them, as had been done in the case of the tannin industry, in 

 the preparation of a satisfactory and uniform method. As a pre- 

 liminary step, samples of fats were sent out to nineteen chemists 

 to find out what methods were in use and how the results obtained by 

 the various modifications would agree. The following directions were 

 sent with the samples of fat: 



State the details of the method employed, size and thickness of test tube used, and 

 capacity of bottle. 



Give saponification value of the fatty acids. 



State the temperature of the room at time of test and the kind and dimensions of 

 thermometer used, especially the size of the bulb. If possible, have the thermome- 

 ter checked against a standard. 



It was found that modifications of two methods were in general use 

 in this country, but that the details of the methods as carried out in 

 the different laboratories were varied and could only lead to diversity 

 of results. It was also found that no definite style of thermometer 

 was used, dimensions of the bulbs varying greatly, some being quick- 

 acting and some slow-acting thermometers. This fact also is bound 

 to affect the results. These two methods gave quite different figures, 

 and no very close agreement was obtained by analysts using the same 

 method. Evidently a uniform method and a uniform thermometer 

 were essential, and it was decided to try for further work two methods 

 which represented the two types in use, namely, the Dalican method, 

 as used by James Boyce, American Cotton Oil Company, and the 

 Wolf bauer method, as used by A. G. Manns, of Armour & Co. 



DALICAN METHOD. 

 APPARATUS. 



A round iron or metallic dish, 1.5 liters capacity. 



A porcelain dish, 2 liters capacity. 



Test tube, 22 mm to 25mm diameter, 15 cm long, the walls of the tube to be 1.6 

 mm thick. 



One bottle, 7.5 cm diameter, 15 cm deep, to have wide mouth, with cork of suffi- 

 cient size to hold test tube. Bottle to be of clear glass, with thick wall. 



A delicate certified thermometer, reading in T V degrees, graduated from to 70 C., 

 bulb of thermometer to be not more than 6 mm in diameter and 3.4 cm long. 



An accurate thermometer to hang alongside of the apparatus to record the temper- 

 ature of the room in which test is made. 



17219 No. 2205 



