I have the 2016 HCPCS Level II Expert. Sodium Chloride is not even listed in the index and I don't see J2912 in the Tabular. Further Sodium Chloride is not listed in the Table of Drugs and Biologicals.
Sodium Chloride is salt. If you look up Saline Solution in the Table of Drugs there are 4 codes for different volumes, etc. and route. They are J7042, J7050, J7030, and J7040. If you look up Saline solution in the index we are directed to A4216, J7030-J7050, and there is an entry for Metered dose dispenser A4218.
I have learned that the index in the HCPCS book, at least the Expert Level, leaves something to be desired, so it is best to use both the Index and Table of Drugs to point you at the codes, then choose the best code for the particular situation you are coding.
Also, I have heard JoAnne Sheehan say she uses the Professional version of the HCPCS. I plan on trying that for 2017 to see if I like it better.
Hope this helps!