Frederick Post 1491 Chemical
The Frederick Post 1491 was fabricated in Japan by the Sun-Hemmi Company and commercialized in the United States by Frederick Post Company from 1956 to 1969. As most of the rules fabricated by Sun-Hemmi, this was also fabricated from a large-diameter variety of bamboo grown in Kagoshima Prefecture on the island of Kyushu, coated on all sides (except the ends) with white celluloid, and held together with metal posts. The glass indicator has a metal frame screwed to plastic ends. The Post 1491 was a clone of the Hemmi 257.
The 1491 was designed for Chemical Engineers as an aid to solve problems involving temperature, pressure, and solution concentration, and was able to solve with one rule setting problems like:
give atomic weights of 52 elements and molecular weights of 18 atomic groups (Ch-scale)
stoichiometric calculations
simultaneous conversion in operations with Centigrade, Fahrenheit, Kelvin or Ranking temperatures.
conversion of pressure units (atmospheres - pounds per square inch - kilograms per square centimetre)
vapor pressure of water at various temperatures
convert concentrations units
compute liquid-vapor equilibrium relationships
relationships between temperature and adiabatic expansion and compression of a given gas
temperature of saturated steam
The rule has also specific marks to show:
Molecular gas constants
Standard molecular volume of ideal gas
Faraday Constant
Correction factor for volume of ideal gases
Mechanical equivalent of heat
The 1491 has 12 standard scales on the front face: L, A, DF [ CF, CIF, CI, C ] D, LL3, LL2, LL1, and on the back side the specialized scales: Ch(A~M), Ch(N~Z), M1 Xw [ M2 X, Temp(F,C,K)°, F(t) ] Kg/cm2, P mmHg Atm, P inHgVac Lb/in2 Gage , tω °C
According with the two-letters code engraved on rule's front face, next to the Sun-Hemmi-Japan logo: GE, the item in this collection was manufactured in May -1956, according with the table at the end of the ISRM Frederick Post page.
Next is a cool simulator of this rule:
With standard scales on the Post 1491 ans skillful user was able to perform most of the next arithmetic operations:
SlideRulePractice-2.pdfThere is a quick reference to use the specialized scales for the twin model Hemmi 257.
ISRM_M384_Hemmi_257_Chemical_SlideRuleInstructions_BelongedToBrianCunninghamAustralia.pdfFor this rule is possible to use as a reference the User Manual for the equivalent model Hemmi 257. here you can see problems solved using the specialized scales:
HEMMI 257-POST 1491 CHEMICAL.pdf
