The General Formula Indexes cover both the main and supplemental volumes and are arranged strictly alphabetical by element symbol (Hill Convention).

It is best to start with the latest Formula Index Supplement, since each supplement published updates the previous edition. There are three columns in the Formula Index. The first column shows the empirical formulas arranged by alphabetical order of the element symbols and by increasing atom count (Hill Convention). The second column show the linear structural molecular formula in classic format as it appears in Gmelin text. The third column provides volume and page numbers to a particular entry.

Example: Look up the compound Cl 2 OU. The formula index entry reads:

Column 1 - Hill Convention mol. formula
Cl2OU

Column 2 - Linear (classic) molecular formula
UOCl2

Column 3 - Element Volume Number and Pagination.
U: SVol.A5-224  (Uranium Supple. Vol. A5, page 224)

In each volume of the Main Work and Supplement Series, there is a table of contents, in which information may also be located.

I can’t read the entry! It’s in German.

Earlier volumes are in German with some English captions. More recent volumes, 1982+, are in English. Use a German-English science dictionary to translate unfamiliar words. All of the foreign language dictionaries are located in the first row of the reference collection.

Patterson's German-English dictionary for chemists [Highly Recommended] 
 Lockwood Science & Engineering Reference QD 5.P3 1992

Cassell's German - English, English - German dictionary 
 Lockwood Science & Engineering Reference PF 3640.B45 1978

Dictionary of chemistry and chemical engineering 
Lockwood Science & Engineering Reference QD 5.D47 1987