220 



used which will hold and yet permit the easy removal of the cover. A mixture of 

 3 parts paraffin (hard) and 5 parts vaselin is satisfactory. These are melted together 

 and then cooled slowly, with continual stirring. If the work is to be done during 

 continued cold weather a little more vaselin may be used, or in summer a little more 

 paraffin. The addition of rubber or Venice turpentine to the lubricant has been dis- 

 continued on account of the difficulty in removing the covers. 



After the filled desiccators have been exhausted, rotate them carefully every three 

 or four hours to mix thoroughly the acid and the water which has been absorbed into 

 the upper portions. Care must be used not to spatter the acid upon the tubes. At 

 the end of twenty-four to forty-eight hours, a? is convenient, allow air to bubble slowly 

 through concentrated sulphuric acid into the desiccator and transfer the tubes to a 

 desiccator provided with fresh acid. Chemically pure sulphuric acid must be used, 

 as the commercial acid discolors the samples. 



Exhaust the freshly filled desiccators and hold for another twenty-four to forty-eight 

 hours, as is convenient. During this interval mix the acid three or four times. Next 

 weigh the tubes and place them in a vacuum again for twelve hours or longer and 

 again weigh, to prove that the drying is complete. If any of the tubes do not show 

 constant weight they are placed in vacuum again with fresh acid. The acid employed 

 for the first drying 'is used for commercial acid; that with which the drying is com- 

 pleted is used as the first acid with fresh samples. 



With blood the freshly drawn sample is rapidly poured into tared tubes filled with 

 fat-free cotton, each tube being placed in a tared weighing bottle. The tui>e and 

 stoppered bottle are weighed to get the weight of the sample, and the moisture is 

 obtained as with meat samples. 



We have demonstrated that this method is capable of practical application to 

 agricultural analyses in general, and is especially to be recommended where a determi- 

 nation of the fat or ether-soluble constituents is to be made. The most marked 

 differences have been noted in fat determinations upon samples of fresh bone (skeleton 

 of beef). When heat has been used in drying the samples by the official method the 

 extracted fats are frequently very dark colored. By using the vacuum method with- 

 out heat the extracted fat is almost snow white. This method has been compared 

 with the regular official method upon numerous other samples, as butter, milk, soil, 

 feed stuffs, honey, soap, etc. A few results are given in the following tables illustrat- 

 ing several phases of the work. 



Moisture determinations on various animal substances by vacuum method without heat. 



Moisture determinations on blood by vacuum method without heat. 

 [Using absorbent cotton and showing effect of second drying in the vacuum.] 



