TEMPERATURE CHANGES, ETC., DURING CANNING OPERATIONS. 13 
TABLE 1.—Maxvimum-pressure tests with No. 8 tin cans containing 100 ¢. c. and 
950 c. c. of distilled water. 
Cis aa 100 c. c. water. | 950 c. c. water. BD 100 c. ec. water. | 950 ce. c. water. 
ale 
Pres- Pres- | Pres- s Pres- 
: Proc- | Barom-|sure per| Barom-| sure per |} «,.};,, | Proc- |Barom- sure per} Barom-|sure per 
Sealing. essing.| eter. |Square| eter. | Square || Sealing. essing.| eter. | square} eter. | Square 
inch. | inch. | inch. inch. 
pinata abe cf ceame | i (aco 
| Lbs. Lbs. || Lbs Lbs. 
100 29. 92 17. 06 30.18 14. 60 | 100 30. 05 10. 67 30.18 9. 88 
109 29. 92 2.70 | 30.18 20. 25 | 70 109 30. 05 16, 26 30. 18 15. 49 
20......- ihe 06 2aO2 28. 23] S018 | ~ 25.40°|/' “o-oo 116 | 30.05 | 21.78] 30.18] 20.74 
121 29.92 | 32.89 30.18 29. 52 121 30. 05 26. 26 30. 18 24. 91 
100} 30.08 | 13.87) 30.15 10. 99 ( 100] 29.95 7.97 | 30.16 7.30 
50 109 | 30.08} 19.51) 30.15 16. 36 | 80 1O9N 295951) 13:37 || 30,16 12.70 
ce eta 116 | 30.08} 25.10] 30.15 21. 44 pears 116} 29.95) 18.95] 30.16 17. 64 
121} 30.08} 29.60; 30.15 25. 02 121 | 29.95) 23.50 | 30.16 21. 66 
CR isso n| el AO | oe. m wralni| cnecete sis 100 | 29.92 4.66 | 30.05 4.41 
60 LOOK) oO sdile (wr Bs O4:,)) Fe ces lenis aa 90 109 | 29.92; 10.12] 30.05 9. 51 
ade es LUGE | Mereilenile pee OO! |e 0 (coc | eclo accel AS Men 116 | 29.92 | 15.46] 30.05 14. 36 
AZ Ne SOLU | Meese lON eo ee cele sacieeee 121 | 29,92 | 20.06 | 30.05 17.79 
Too much importance, of course, should not be attached to one set 
of figures, as results with individual cans vary somewhat, but the 
outstanding features shown here have been confirmed by repeated 
experiments, and the figures presented closely approach the average. 
Leading facts disclosed—F¥rom all these tests the following facts 
seem clear: 
(1) With water the pressures developed are always below the 
theoretical (that with some food materials this does not hold in all 
cases will be shown later). 
(2) The higher the retort temperature, the greater the variation 
from the theoretical pressures. 
(3) The higher the initial temperature, the nearer to the theoreti- 
cal does the pressure come. 
(4) The larger cans show a somewhat greater divergence from the 
theoretical values than the smaller. 
(5) With water, the smaller the head space the less the experi- 
mental pressures obtained. The fact that with water the smaller the 
head space the less the experimental pressures obtained is likewise 
borne out by experiments with No. 2 cans, using 50 and 550 ¢. ¢. of 
water, the tabulation of the results of which is omitted for lack of 
space. 
Influence of head space-——With cans entirely filled and sealed at 
any temperature below 100° C. the experimental pressures have been 
found less than where a head space was allowed. This is explained, 
of course, by the fact that under these conditions the prime factors 
operating are vapor pressure and expansion of the water, whereas 
when a head space is allowed the air pressure also contributes to the 
