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:

https://www.sliderules.org/react/hemmi_257_chemical.html 

Here is a very interesting article from the Oughtred Society about the Chemical Slide Rules:

 http://www.oughtred.org/jos/articles/V21.2_p08-15.pdf