The Techniques of Holocaust Denial

Writer: Richard Green

Page 32 of DuPont's Hydrogen Cyanide: Properties, Uses, Storage
and Handling^{1} contains a plot of the partial pressure of HCN
above aqueous solutions of HCN at various concentrations and temperature.
These values are equilibrium values. That means that at these
concentrations the rate of HCN in the gas phase becoming absorbed into
the solution is exactly balanced by the rate of HCN leaving solution
into the gas phase.

Because the plot shows equilibrium values, it contains implicitly the
value of partition coefficients, *i.e.*, it is possible to obtain
the equilibrium concentration of HCN in solution in water exposed to HCN
in the gas phase as a given concentration and temperature. This
appendix extracts those values. In DuPont's plot liquid phase
concentration is expressed in weight percent and gas phase concentration
in millimeters of mercury (also known as Torr); this appendix derives
relationships in terms of molarity (M) and grams per cubic meter
(g/m^{3}).

These values are equilibrium values, which means that they are an upper limit to the concentration that may be found in water exposed to HCN. How fast such equilibrium establishes itself is a question of kinetics and is a much more difficult problem.

By reading the values for a given temperature from the plot, one can construct a plot of the weight percent HCN in water as a function of gas phase concentration in Torr. The relationship is linear in the region of interest; so intermediate values can be found by fitting the points with a least-squares linear regression. At 0 Torr, the concentration in water should be 0%; therefore the fits have only one free parameter, the slope. This linear relationship is known as Henry's Law and the slope can be identified with the Henry's Law constant.

Figure I.1 shows such a plot for a temperature of 30 degrees Celsius (° C). The points have been read by eye from DuPont's plot. Notice that the fit to a line is excellent and is likely to average out slight deviations in the estimates of values in DuPont's plot. The slope in this case was found to be 0.029 percent/Torr.

Similar plots were made for 0, 10, 20, 30, 40, and 50 degrees. The values of the slope were:

Table I.1: Slope of the Gas-Liquid Partition as a Function of Temperature. | ||
---|---|---|

Temperature | Slope. | |

° C | percent/Torr | |

0 | 0.105 | |

10 | 0.066 | |

20 | 0.047 | |

30 | 0.029 | |

40 | 0.020 | |

50 | 0.013 |

The problem is now essentially solved except for unit conversions.
DuPont's liquid phase concentration is expressed in weight percent, and
I wish to express that value in molarity (M). The first step is to
calculate what volume of water contains 1 mole of HCN. The
molar mass of HCN is 27.03 g. The mass of water
(M_{H2O}) can be expressed as:

(Mwhere C is the concentration in weight percent HCN. The density of water is 1.0 g/mL and will be treated here as independent from temperature. HCN density as a function of temperature was found by a linear extrapolation of the densities found on page 2 of the same DuPont document. The fit in g/mL yielded:_{H2O}) = (100/C -1) x 27.03

pwhere T is expressed in degrees Celsius (° C), and p_{HCN}=0.715-0.00133 x T

V= 27.03/pI convert to molar concentration:_{HCN}+ M_{H2O}/1.0

[HCN] = 1000/VThe gas phase concentrations of in the gas chamber were in the range of 8-16 g/m

P=R x T x (C/27.03) x (760/101325)Here P is the partial pressure of HCN in Torr. R is the universal gas constant (8.31441 m

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