VOL. 2. NO. 3
APPLICATIONOB SLmE RULETO CEEMICAL ATI IONS
209
THE APPLICATION OF THE SLIDE RULE TO CHEMICAL CALCULATIONS PROP.W. T. GOOCK, BAYLORUNIVERSITY, WACO, TEXAS The Slide Rule is adapted to many computations and for approximate results is valuable on account of the time saved. The accuracy is sufficient for almost all practical requirements and this is especially true of elementary chemical calculations. The methods and instructions for operating the slide rule are furnished with the rule and will not be repeated here. However, a scheme for its use in working gas problems rapidly will be given for the aid of those who may care to apply it. The author is a strong advocate of the slide rule in teaching chemistry calculations and checking students' work and has found it great help in the class room demonstration of chemical problems. In working proportions, as for example 38.6 : 77.2 :: 4.7 : x, the first and third terms are set on the D scale and over them on the C scale, the second and fourth terms. Thus the value x would be found on the C scale over the third term 4.7 if the second term 77.2 is set over the first term 38.6. Diagram: C Set 77.2 , Read x D I Over 38.6 Over 4.7
I
In working the problems involving the application of Boyle's and Charles' laws the methods of statement of each problem as outlined in Type I must be made first as
Let the three numerators in the statement be designated by V, P and T,respectively, and the denominators by P' and T'. Then the steps in the calculation are as follows: Set V on the D scale and over it set P' on the C scale. Then move the runner to P; next move the slide until
T' is under the runner; then move the runner to T,and under that on the D scale read the resu1t.V'. This may be diagrammed in this manner: C Set P' 1 Runner to P I Slide T' to runner I Runner to T D Set V
I
I Read V'
Thus all the volumes are found on the D scale and the temperature and pressure factors on the C scale. The author's slide rule has the positions 273 and 760 marked on the C scale and the position 22.4 on the D scale with red ink. The author has been able to find the result-of a prohlem like that given above in less than twenty seconds with the slide rule. -P. 26 from "Typical Calculations in Elementary Chemistry," by W. T. Gooch. Baylor University Press, 1923.
