80 BULLETIN 846, U. S. DEPARTMENT OF AGRICULTURE. 



Knorr Apparatus vs. Johnson Apparatus for Ether Extract Determination. 



As many food laboratories are equipped with the Johnson appa- 

 ratus but not with the Knorr apparatus, which has almost invariably 

 been recommended for egg work, a comparison of results using the 

 two was made, extracting in all cases for 3 hours. 



Table 31. — Percentage of ether extract obtained by using Knorr apparatus and Johnson 



apparatus. 





Initial of analyst. 



Knorr. 



Johnson. 



Sample 

 No. 



Using 



2.5± 



grams. 



Using 



5.0± 



grams. 



Using 

 2.5± 

 grams. 



Using 



5.0± 



grams. 





(B 



Per cent. 

 10.64 

 10.54 

 10.51 

 10.31 

 10.60 

 11.16 

 11.56 

 10.88 

 11.33 

 12.36 

 13.12 

 13.00 

 11.63 

 11.76 

 11.57 

 11.34 

 11.57 

 6.07 

 5.59 

 5.94 



Per cent. 

 10.72 

 10.46 

 10.52 

 10.44 

 10.52 

 11.15 

 11.58 

 9.89 

 11.14 

 12.47 

 12.85 

 12. 63 

 12.90 

 11.75 

 11.50 

 11.46 

 12.41 

 5.84 

 5.59 

 5.90 



Per cent. 

 10.74 

 10.46 

 10.30 

 10.13 

 10.70 

 11.18 

 12.78 

 10.64 

 11.33 

 12.44 

 12.65 

 12.60 

 11.97 

 11.71 

 11.50 

 11.55 

 11.42 

 5.83 

 5.59 

 5.91 



Per cent. 

 10.70 





D 



10.51 



16 



^E 



10.41 





H 



10.17 





Is 



10.46 





f B 



11.22 





D 



11.46 



18 



H 



10.81 





Is 



11.18 





fD 



12.45 





E 



12.84 



1 



H 



12.82 





(s i 



12.11 





m 



11.54 





E 



11.47 



3 



H 



11.42 





[s 



11.32 





ID 



5.67 



15 



H... 



5.42 





is 



5.88 











10.57 



10. 53 















It is evident that the Johnson apparatus may be substituted for 

 the Knorr apparatus, although the Knorr should always be used if 

 possible. 



Effect of Time of Extraction upon the Ether Extract Determination. 



Nothing is gained by prolonging the extraction for more than 3 

 hours, as is shown by the results given in Table 32. 



Table 32. — Percentage of ether extract obtained during varying periods of extraction. 



Sample 



No. 



Extracted 

 3 hours. 



Extracted 

 16 hours. 



3972 



Av 



Per cent. 



( 10.24 



10.13 



1 10. 23 



I 10.15 



Per cent. 

 10.40 

 10.22 

 10.32 

 10.22 



10.19 



10.29 



