User Manual

3 - 3
IPN 074-289L
Composer Operating Manual
to a range of about 1.1 to 1.7 for almost every known gas. Consequently,
guesses that are wrong don’t make a lot of practical difference if they are
reasonable guesses. It is also possible to make intelligent guesses about
unknown gasses using the value of the Specific Heat Ratio for a similar gas.
Interestingly, it is almost always more accurate to overestimate the Specific
Heat Ratio than to underestimate by the same amount; see Table 3-1 and
Figure 3-1. Consider also that in production the accuracy is not as important as
the reproducibility. As long as the Specific Heat Ratio is not changed the
Instrument System will reproduce the results day after day.
Table 3-1 Common Molecular Weights and Specific Heat Ratios
Gas Name
Molecular
Weight
Specific
Heat
Ratio Gas Name
Molecular
Weight
Specific
Heat
Ratio
Ammonia
(NH
3
)
17.030 1.316 R134a 102.000 1.120
Argon 39.948 1.667 SiBr
4
347.702 1.094
AsH
3
77.950 1.269 SiCl
4
169.900 1.101
B
2
H
6
27.670 1.165 SiF
6
142.080 1.127
CBr
4
331.627 1.100 SiFH
3
50.1 1.213
CO
2
44.010 1.288 SiHCl
3
135.450 1.123
Cp
2
Mg 154.49 1.2 TEAM - DMZn 196.65 1.10
Cupra-select 370.830 1.052 TDEAT 336.10 1.2
DETe 185.72 1.100 TDMAT 224.0 1.2
Deuterium 4.032 1.398 TEGa 156.910 1.103
DMHy 60.10 1.16 TEOS
Si-(C
2
H
5
O)
4
208.26 1.2
DMZn 95.450 1.120 TMAl 72.090 1.230
Ethyl Lactate 118.100 1.140 TMGa 114.830 1.103
GeCl
4
214.404 1.097 TMIn 159.930 1.120
Helium 4.003 1.630 WF6 297.830 1.075
Hydrogen 2.016 1.404
Nitrogen 28.010 1.399
Oxygen 32.000 1.395
POCl
3
153.33 1.168