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From this, it is obvious that in order to have the average of four measurements of the specific heat reliable to less than 1%, a roll of film should have a mass of 500 grams and the temperature of the oven should be at least 15 to 18 degrees above the final temperature of the calorimeter. If the weight of the film be greater than 500 grams, and the temperature change of the film greater than 12 degrees, then the percentage deviation of a single determination would be less than 1.58%. It is not advantageous, however, to have the initial temperature of the film too high, since under such conditions the loss of heat at the sprocket, over which the film was passed before entering the calorimeter, will increase because of the increased temperature gradient between the film and sprocket. It is estimated that 45°C is the practical limit, and this is well below the kindling point of the film.
Table No. 3 Detailed data on specific heat of motion picture film.
Trial No. 7 (Table 7)
Base: Cellulose Nitrate
Mass of Film: 552 grams Optical density (average) : 0.56
Time in oven: 100 hours
Sprocket speed: 108 feet per minute
Calorimeter Temperature rise: 2.38°C.
ime
Relative Time in
Temperature
minutes
Calorimeter
Oven
9.00
0
22.29
39.98
.05
5
.40
.75
.10
10
.50
.64
.15
15
.58
.82
.20
20
.66
.76
.25
25
.74
.96
.30
30
.82
.90
.31
31
23.00
31.5
.64
34. 83 Mean
.32
32
24.34
32.5
.60
.33
33
.80
33.5
.90
.34
34
25.06
34.5
.12
.35
35
.15
35.5
.16
.36
36
.16
36.5
.14
.37
37
.12
.38
38
.08
.39
39
.03
.40
40
24.98
.42
42
.90
.44
44
.84
.46
46
.79
.48
48
.76
.50
50
.73
.55
55
.66
.60
60
.62
10.05
65
.58
.10
70
.56
.15
75
.54
.20
80
.52
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