TEMPERATURE CHANGES, ETC., DURING CANNING OPERATIONS. 9 



CONCUSSION TESTS. 



The apparatus illustrated in figure 2 was employed in the con- 

 cussion tests. 



This apparatus consists merely of an ordinary laboratory ring- 

 stand support, the standard of which is graduated in centimeters. 

 The adjustable ring supports a wooden block, which is sawed 

 lengthwise to allow the entrance of a fine copper wire attached to a 

 weighted can. A metal pin in this block holds the wire until ready 

 for release. The test can is placed on the platform at right angles, 

 with the weighted can suspended above in such a way that the weight 

 in falling strikes it midway between the ends. The weight is raised 

 to the desired height by adjusting the ring. The weight is prepared 

 by cutting a hole in the side of an ordinary No. 2 can with both 

 ends crimped on and running into it the required quantity of molten 

 lead while the can is lying on its side. This, in addition to furnish- 

 ing the required weight, lends rigidity to the can and prevents its 

 denting. In these tests the over-all weight of the can was 635 grams, 

 which corresponds closely to the weight of an ordinary No. 2 can 

 of food. 



With this arrangement the can of food to be tested may be sub- 

 jected to the most rigid treatment and will thus give an index to 

 its relative resistance to handling when subjected to variable 

 exhausts. 



CONTAINERS. 



The containers used in these tests were the standard packers' cans. 

 Because of their adaptability for ready attachment to the other 

 apparatus the hole-and-cap type, with ends mechanically crimped 

 on, was employed for the most part, though the cans used for the 

 concussion and rough vacuum tests described later were of the 

 open-top type. The great difficulty in finding cans with air-tight 

 seams made it necessary in all cases where great accuracy was re- 

 quired to solder all ends over the seam before making a test. In 

 the canning tests covered by this and other studies during the last 

 season, as high as 18 to 20 per cent of the cans have been found to 

 show visible leaks at the factory ends when they were taken from 

 the retort. It is to be expected that small leaks will show up when 

 great pressures are developed, but certainly visible leaks should 

 not appear to this extent where common canning practices are em- 

 ployed, as was true in these cases. 



THEORETICAL PRESSURES AND VACUUMS. 



The development of pressure and the formation of vacuum fol- 

 low the well-known physical laws for gases and saturated vapors 

 with changes of temperature. A consideration of the theoretical 

 70344°— 22 2 



