Parr-instrument 1341 Bedienungsanleitung PDF herunterladen (Seite 8)

1341 Plain Jacket Calorimeter

Parr Instrument Company

8

Calculating the Heat of Combustion

Assembly of Data

The following data should be available at the com-

pletion of a test in a 1341 calorimeter:

a = time of ﬁring

b = time (to nearest 0.1 min.) when the

temperature reaches 60 per cent of the

total rise

c = time at beginning of period (after the

temperature rise) in which the rate of

temperature change has become con-

stant

t

a

= temperature at time of ﬁring

t

c

= temperature at time c

r

1

= rate (temperature units per minute) at

which the temperature was rising during

the 5-min. period before ﬁring

r

2

= rate (temperature units per minute) at

which the temperature was rising during

the 5-min. period after time

c. If the temperature was falling instead

of rising after time c, r is negative and

the quantity -r (c-b) becomes positive

and must be added when computing the

corrected temperature rise

c

1

= milliliters of standard alkali solution used

in the acid titration

c

2

= percentage of sulfur in the sample

c

3

= centimeters of fuse wire consumed in

ﬁring

W = energy equivalent of the calorimeter,

determined under standardization

M = mass of sample in grams

Temperature Rise

Compute the net corrected temperature rise, t, by

substituting in the following equation:

t = t

c

- t

a

- r

1

(b-a) - r

2

(c-b)

Thermochemical Corrections

Compute the following for each test:

e

1

= correction in calories for heat of forma-

tion of nitric acid (HNO

3

)

= c

1

if 0.0709N alkali was used for the

titration

e

2

= correction in calories for heat of forma-

tion of sulfuric acid (H

2

SO

4

)

= (13.7) (c

2

) (m)

e

3

= correction in calories for heat of combus-

tion of fuse wire

= (2.3) (c

3

) when using Parr 45C10 nickel

chromium fuse wire, or

= (2.7) (c

3

) when using No. 34 B. & S. gage

iron fuse wire

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