16 ‘BULLETIN 1022, U. S. DEPARTMENT OF AGRICULTURE. 
TABLE 4.—IJncrease in the volume of water in No. 2 and No. 3 tin cans when 
processed at different temperatures, the initial volume in No. 2 cans aa 30 
c.c. and in No. 3 cans, 950 ¢. &. 
[Based on Smithsonian tables.] 
NWewmwW WONN OWOH 
\ 
° | Volume (c. ¢.). 
Temperatures (° C.). 
No. 2 cans. No. 3 cans. 
a 
Sealing. | rae Total. | Increase. | Total. “Inerease. 
| | | 
fy 100 | 5728] 228] 999.4] 29. 
= 1) p 110°) | bel 27 2 oe 47, 
Fa oe 9 = OS ) 115.5) 579.7 29.7 | 1,001.3 | 51. 
A Whi) 585.3) 35.3) 1010.9 | 60. 
100 561.1/ 11.1] 969.2] 19, 
Ss 110 565.4| 15.4| 976.7 | 26. 
pevtsiea fo ker grist oa + iy manatee wear enc oRe 115.5 | — 567.9 17.4| 984.9 | 34, 
|Reeb Tee raw gp 23.3 | 990.3 | 40. 
| 100 557.7 | 7.7| 963.3 | 13. 
Fe e910, |. 62 Oe a OP SG 20. 
ee ee ee ) 115.5| 5644] 444] 99749]. Oe 
| 121.1] 569.8, 19.8] 984.2 | 34. 
j J 1 
Relation of barometric pressure.—A. factor of considerable impor- 
tance concerned with vacuum in cans is the barometric pressure, 
especially as related to differences in altitude. Table 5 shows the 
differences in barometric pressure for altitudes ranging from sea 
level to approximately 6,000 feet and how, for example, food ma- 
terials packed at or near sea level would lose in vacuum by over 3 
inches, under identical temperature conditions, when shipped to a 
place 3,000 feet above sea level. This loss would be increased, of 
course, if those shipments were made to hot climates or during the 
summer. 
TABLE 5.—Barometric pressure for different altitudes. 
[Taken from Smithsonian Meteorological Tables, 4th rev. ed., 1918, pp. 136-137.] 
| : | 
Baro- Baro- || Baro- 
Baro- 
2 metric | “= metric . metric ee metric 
Altitude. pres- Altitude. pres- || Altitude. pres- Altitude. pres- 
: sure. | sure. | sure. ; sure. 
REE 61 Ga, a BE Gen on 
0 (sea level)....| 29.90 || 607 feet.........| 29.24 || 1,504 feet?...... 28.29 || 3,998 feet......- 25. 81 
AM FeCh 225. 22 29. 79 IO0TESES. 2.2222 29. 14 || 1,999 feet......- 27.78 || 4,498 feet......- 25. 34 
210 feck. -3 -1— 29:68 | S3i eet =.= al: 2 9 03: el B02 feeie 2 27.27 || 5,006 feet......- 24. 80 
Uae (ee 29.57 || 906 feet......... 28. 92 3,005 fects tes 26.77 || 5,503 feet. .....- 24. 42 
AQ feet 29. 46 | 1,000 feet. ...... | 28.82 || 3,497 feet....... 5,997 feet. =.= = 23. 9& 
505 feet-.--.....] 29.38 || . | | 
} 1] | | } 
While these matters may not be of-great importance it is probable 
that the unfortunate experience of some canners has been due to some 
of these factors or to a combination of them. 
VACUUM STUDIES. 
Vacuum readings obtained in tests—To determine how closely ex- 
perimental results with tin cans would agree with the theoretical 
