TEMPERATURE CHANGES, ETC., DURING CANNING OPERATIONS. 15 



Of less importance also is the influence of the linear expansion of 

 the metal of the can, due to the rise in temperature. 



Another fact of much importance in connection with all pressure 

 and vacuum tests is that individual cans vary considerably in their 

 resistance to pressure, whether internal or external. This fact 

 accounts in part for some of the irregularities in the experimental 

 data presented. 



Expansion of water. — The expansion of the water. due to the rise 

 in temperature likewise has some effect upon the pressure developed. 

 This, while unimportant where the quantity of water is small, may 

 have a considerable influence where the head space is reduced to a 

 minimum', as decreasing the volume of gas in the head space by one- 

 half through expansion of the water after sealing theoretically 

 doubles the pressure developed by the expansion of the inclosed air. 



In Table 1 no corrections have been made for this expansion. The 

 tendency, however, is always to increase the variations between the 

 experimental and the theoretical figures. 



Table 3, which has been taken from the work of standard authori- 

 ties (see Smithsonian Physical Tables, Fowle, 7th revised edition, 

 1920, p. 120 ; also Kent's Mech. Eng. Pocketbook, 9th edition, 1916, 

 p. 716), shows the increase in volume of a unit quantity of water 

 when passing through the range of temperature with which the pres- 

 ent work is concerned. 



Table 3. — Volume of water at different temperatures. 



[The mass of 1 cubic centimeter at 4° C. is taken as unity.] 



Temperature (° C). 



Volume. 



Temperature (° C). 



Volume. 



Temperature (° C). 



Volume. 







1.00013 

 1.00000 

 1.00001 

 1.00027 

 1. 00087 

 1. 00177 

 1. 00293 

 1. 00434 

 1. 00598 



1 40 



1.00782 

 1.00985 

 1. 01207 

 1. 01448 

 1.01705 

 1.01979 

 1. 02270 

 1. 02576 

 1. 02899 



85 



1. 03237 



4 



! 45 



90 



1. 03590 



5 



| 50 



95 



1. 03955 



10 



55 



100 



1. 04343 



15 



60 



110 



1. 0515 



20 



1 65 



115.5 



1. 0560 



25 



70 



121.1 



1.0661 



30.. 



75 







35... 



80 











Table 4, which is based upon the foregoing, shows the actual in- 

 crease in volume of water in No. 2 and No. 3 tin cans when sealed 

 at various temperatures and processed at 100°, 110° 115.5°, and 121.1° 

 C, the initial volume of the water in the No. 2 can being taken as 

 550 c. c. and in the No. 3 as 950 c. c". The figures are self-explanatory. 



