First Work: Properties of Coal at BCURA Part II

The director of research at BCURA (the ​British Coal Utilisation Research Association) was Dr. Donald Bangham, whom Franklin coauthored a journal article with ("Thermal Expansion of Coals and Carbonised Coals," 1946, shown right).

Franklin and Bangham were researching the thermal expansion of solid coal and charcoal. Thermal expansion is how substances change their shape and size with temperature, usually not including phase changes (eg. changes between water, liquid, and gas). Usually we look at thermal expansion in gasses (such as when a sealed balloon shrinks in the cold and gets bigger in the warmth), however, Franklin and Bangham were looking at the thermal expansion of solids. (While we don't think about it as much we still do see this in our everyday lives. A common example of this is pavement contracting in the winter and resulting in potholes in the spring.)

"Thermal Expansion of Coals and Carbonised Coals" by D. H. Bangham and R. E. Franklin, 1946*

Franklin and Bangham were looking at how the thermal expansion of charcoal and coal was affected by the amount of methanol was saturated in the coal or charcoal. The expansion of charcoals with the absorbed films of alcohols is harder to measure since it's very complex: at first it expands much faster than dry charcoal, but then it shrinks before expanding again due to the moisture evaporating from it. Franklin and Bangham devised a method to measure this more accurately by a method of preheating the coals to high temperatures.  

After this paper was published, Franklin published her own journal article in 1948 ("A Study of of The Fine Structures Of Carbonaceous Solids by Measurements of True and Apparent Densities: Part I. Coals," 1948, shown below) which detailed her experiments in apparent density of coals at BCURA.

"A Study of The Fine Structures Of Carbonaceous Solids by Measurements of True and Apparent Densities: Part I. Coals" by Rosalind E. Franklin, 1948**

In this Franklin was studying the properties of pores of coals with varying carbon contents using measurements of true and apparent densities. True density is the actual density of a material. The apparent density, on the other hand, is the density measured using the volume of a liquid or gas displaced by the material. This works because the fluid should fill the holes in the sample of the material so it doesn't matter the material's shape. However, if the pores of the material are small enough, as they were with the coal samples in Franklin's experiment, the molecules of the fluid might not physically fit into the pores. Smaller molecules will fit into smaller pores while bigger ones will not, resulting in different apparent densities when measuring with different size molecules. The pore size not only affects the apparent densities when using different molecules, but also how fast they can seep into the pores. Franklin measured the apparent density of a coal in a particular fluid over time, not just at first, which allows molecules time to seep into the pores. This change in apparent density is called the drift.

Smaller molecules (helium is a great) give apparent densities closer to the true densities of materials. No matter how small of a molecule you use, however, it will not fill completely closed off holes in the material.

The fluids Franklin used in her experiment were helium gas, methanol, water, n-Hexane, and benzene. The chemical structures of these gasses and liquids are shown in the above order below. (Note: If you are not familiar with Lewis Structure notation, in short, the two dots represent unbonded electrons and the lines represent bonds. (The triangle shapes in the structure for n-Hexane indicate 3D shape.))

Image credits, from left to right: 1. www.chemistrylearner.com/helium.html, 2. web.chem.ucla.edu/~harding/IGOC/M/methanol.html, 3. socratic.org/questions/5495372e581e2a1c2d5edb9f, 4. socratic.org/questions/595fa291b72cff185f0768e2, 5. arstechnica.com/science/2017/02/researchers-individually-craft-molecules-of-a-reactive-triangular-chemical/

The second part of Franklin's article, "A Study of of The Fine Structures Of Carbonaceous Solids by Measurements of True and Apparent Densities: Part II. Carbonized Coals" (shown below) was published in 1949.

"A Study of of The Fine Structures Of Carbonaceous Solids by Measurements of True and Apparent Densities: Part II. Carbonized Coals" by Rosalind E. Franklin, 1949***

In this article, she details her experiments studying cokes (carbonized coals) using apparent density measurements, again using a variety of liquids and gasses. She compared this apparent density data for varying types of cokes carbonized in a range of carbonization temperatures. 

This molecular sieve property which Franklin observed in these experiments, is of great importance today, as I mentioned previously. In part II, Franklin writes on several occasions that this property must be very important. In her abstract she wrote "This molecular sieve structure must be of importance in determining both the chemical behavior of the solid and the composition of the gas evolved during carbonization." In addition, in the last part of her results section, "Molecular Sieve Properties of Carbonized Coals," which specifically focuses on this property, she again writes how she believes the molecular sieve properties are of great importance.

Sources

* Full citation: Periodical. Bangham, D. H., and Rosalind Franklin. "Thermal Expansion of Coals and Carbonised Coals." Transactions of the Faraday Society 48, (1946): 289-295. Article. 7 Images.. Transactions of the Faraday Society

** Full citation: Periodical. Franklin, Rosalind. "A Study of the Fine Structure of Carbonaceous Solids by Measurements of True and Apparent Densities: Part I. Coals." Transactions of the Faraday Society 45, (1949): 274-286. Article. 13 Images.. Transactions of the Faraday Society
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​*** Full citation: Periodical. Franklin, Rosalind. "A Study of the Fine Structure of Carbonaceous Solids by Measurements of True and Apparent Densities: Part II. -- Carbonized Coals." Transactions of the Faraday Society 45, (1949): 668-682. Article. 15 Images.. Transactions of the Faraday Society