Our transcribers have encountered a possible contradiction between Nemeth Code and Chemical notation. Please see the attached Word document to help us resolve the apparent difference in a Nemeth rule and an example found in the Braille Code for Chemical Notation 1997.
Also, please direct us to any errata for the Braille Code for Chemical Notation 1997 or provide informaton on any plans to update.
Hello and thank you for your question. You have discovered one of the differences between the Chemistry code (CC) and the Nemeth code (NC), namely that when following the CC, abbreviations are spaced as they are in print ... but when following the NC abbreviations are spaced according to specific spacing rules in Rule VIII of that code. Other differences between the two codes, as well as this one regarding abbreviations, are listed on page ix in the introduction to the CC. In section 9, spacing rules for abbreviations are further discussed. 9.1(5) applies here: "Space as in print." The example you cite is in this section and illustrates an unspaced abbreviation "C" (Celsius) -- the abbreviation is unspaced in print and in the braille transcription. The second "C" illustrates the fact that abbreviations are punctuated mathematically in the CC -- another difference from the NC.
Note the two appearances of the abbreviation "g" (gram) in this print example. Clearly this abbreviation is spaced in print. The braille transcription also shows it to be spaced, now requiring the ELI.
The reason the final "C" in this example is spaced in braille is because it follows a sign of operation (NC Sec.54b and CC Introduction, final paragraph).
There is no errata for the Braille Code for Chemical Notation 1997; no errors have been reported. Please continue to ask questions when you don't understand a rule in that code -- it does require careful study in order to apply correctly. Learn from the rules, not only from the simbraille examples.