Historical question concerning Moseley's experiment

[jdlawlis]

This question may be beyond the scope of this forum, but I'll give it a go anyway. Moseley's landmark experiments in 1913 related the square root of the frequency of characteristic X-rays of an element to integer values, which he equated to the element's atomic number. He measured the wavelength of this X-ray radiation using a Bragg diffractometer equipped with a potassium ferrocyanide crystal. My question is why he would choose a complicated crystal structure like potassium ferrocyanide instead of something simpler such as NaCl? I highly recommend the following website, which has an online version of Moseley's original paper:

http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Moseley-article.html

 

[Gokul43201]

My question is why he would choose a complicated crystal structure like potassium ferrocyanide instead of something simpler such as NaCl?

Mostly, I imagine, the reason would have been to maximize signal to noise ratio. So, you want a highly planar single-crystal surface and you want reasonably strong reflections of characteristic lines at angles where reflection of Bremsstrahlung is small. ie: You want a high structure factor for the right plane spacing (to ensure the latter) and you want the planes with these spacings to be cleavage planes of the crystal (for the former requirement).

 

[ravenprp]

There are a few possible reasons why Moseley may have chosen to use potassium ferrocyanide instead of a simpler crystal structure like NaCl for his experiments.

One reason could be that potassium ferrocyanide has a more well-defined and uniform crystal structure compared to NaCl. This would have allowed for more precise measurements and less interference from impurities or defects in the crystal structure.

Another reason could be that potassium ferrocyanide has a higher density and atomic weight compared to NaCl, which may have made it a better choice for studying the heavier elements that Moseley was focusing on. This would have allowed for more accurate measurements and a wider range of elements to be studied.

Additionally, potassium ferrocyanide has a unique property of being able to absorb X-rays at specific frequencies, which would have made it a suitable choice for Moseley's experiments. This absorption property would have allowed for more precise determination of X-ray wavelengths and ultimately, the atomic numbers of the elements.

It is also worth considering that Moseley may have had access to potassium ferrocyanide crystals at the time of his experiments, making it a convenient choice for his studies.

Overall, while NaCl may have been a simpler crystal structure, potassium ferrocyanide likely offered more advantages and capabilities for Moseley's specific experiments on X-ray wavelengths and atomic numbers.