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(SR-52) Gas & Vapor Concentration - SlideRule - 03-31-2020 12:09 AM
An excerpt from American Industrial Hygiene Association JOURNAL (38) 3/77, Gas and vapor concentration calculations by means of a programmable calculator, MARVIN WEINGAST, National Starch & Chemical Corp., Health & Safety Laboratory pgs 147-148
"introduction
The computation of the concentration of a gas or vapor which resulted from the volatilization of a liquid in a confined space lends itself to the use of the programmable calculator. Typical uses of these calculations are the preparation of gas or vapor standards or the determination of the expected vapor concentration resulting from a spill.
Hand-held programmable calculators give the industrial hygienist in the laboratory or in the field the capability of automatically solving complex computational problems.
Once a program is entered into the calculator it can be stored for future use on small magnetic cards. Following the insertion of a program card into the instrument, the data is then entered. The computational instructions are carried out by the calculator after the final data is entered.
Currently two such instruments are available, the Texas Instruments SR-52 and the Hewlett Packard HP-65. This paper will deal with the former.
computation
One of the most common numerical computations used in industrial hygiene is the
determination of the vapor concentration of a volatile liquid that has evaporated in a confined space of known volume. Typical of this calculation would be the preparation of a gas standard or the prediction of the vapor concentration in a room where a known amount of a solvent has been spilled.
The formula used is based on the Perfect gas law:
│W│ × │760│ × │T + 273.2│ (1)
C = 24.47 x 10^6 │m│ × │ p │ × │ 298.2 │
Where C = Concentration, parts per million by volume
W = Weight of liquid, grams
M = Gram molecular weight of liquid
P = Ambient pressure, torr
T = Ambient temperature, °C
Formula (1) can be simplified:
│W│ × │273.2 + T│ (2)
C = 24.47 x 10^4 │m│ × │ p │
Note that:
W=DV (3) (3)
Where D = Specific gravity of liquid
V = Volume of liquid, ml.
The calculated concentration, C, may be expressed in terms of percentage, P:
P = C/10^4 (4)
Program
LBL A STO 01 HLT
LBL 8 STO 02 HLT
LBL C STO 03
(RCL 01 × RCL 02) + RCL 03 X² √x = STO 04
((RCL 01 × RCL 02) - RCL 03) IF ZERO 1'
RCL 04 = STO 05
GTO 075
LBL 1' RCL 04 ÷ 2 = STO 05 HLT
LBL D STO 06 HLT
LBL E STO 07 HLT
LBL A' STO 08 HLT
LBL B' STO 09 HLT
6.2365 EE4 × RCL 05 × (273.2 + RCL 06)
÷ RCL 07 ÷ RCL 08 ÷ RCL 09 = STO 10 HLT
LBLE' RCL10 ÷ 1 EE 4 = ST0 11 HLT
procedure
After the program is fed into the calculator via a magnetic card, the data is entered. Zero is entered if some required data is not available. After each data entry one of the program defined keys (A, B, C, etc.) is pressed. After all seven entries are made the RUN key is pressed. The concentration in parts per million is then displayed. Conversion to percent is obtained by using the E' key.
If there is insufficient data to complete the calculation, zero or a flashing number will appear in the display.
STEP DISPLAY
1. Enter program Blank
2. Enter volume of liquid, ml. Data entered
3. Press A Key Same as Step 2
4. Enter density of liquid Data entered
5. Press B key Same as Step 4
6. Enter weight of liquid, rng. Data entered
7. Press C key Same as Step 6 or calculated weight
8. Enter ambient temperature, °C Data entered
9. Press D key Same as Step 8
10. Enter ambient pressure, Torr. Data entered
11. Press E key Same as Step 10
12. Enter gram molecular Data entered
weight of liquid
13. Press A' key Same as Step 12
14. Enter volume of container Data entered
or room, cubic liters
15. Press B' key Same as Step 14
16. Press RUN key Calculated concentration, ppm (vol.)
Optional step:
17. Press E' key Calculated concentration, % (vol.)
NOTE: If data is not available, enter 0
Current demand for industrial hygienists makes theirs one of the fastest growing professions in today's job market."
BEST!
SlideRule