The Chemistry Code switch indicator has not been approved by BANA.
In the near future, BANA will approve and post "Provisional Guidance" for brailling chemistry in a UEB context. Then transcribers will have definitive guidelines to follow until our codebooks can be updated.
If you are in the midst of transcribing a text, and you have been using the Chemistry Code switch indicator, it is not necessary to change your transcription now. We suggest that you finish out the transcription as you started it.
For new transcriptions of Chemistry in a UEB context, please use BANA's "Provisional Guidance" for Chemistry in UEB. (This will likely include use of the Nemeth switch indicator, with unique chemistry braille symbols listed as special symbols. The chemistry formats are followed but need not be mentioned to the reader.)