Expert: George Maxwell - 8/9/2007

Question
Hi there!
I was reading through a catalogue of chemicals and came to Hydrochloric Acid. Some of the acids had PL, and some had GL next to the name. Also, alot of them had SG1.16 next to them. What do these terms mean? Here they are in context:
256-2.5L GL Hydrochloric acid 32% UNIVAR, SG1.16g" $46.00
and
256-2.5L PL Hydrochloric acid 32% UNIVAR $46.00
Cheers!
Josh

Answer
Hi, and thank you for your question.

It sounds like the initials  you quote are details of purity or "grade" of chemical. Without knowing the company who issues the catalogue I can't be sure, but the GL and PL look very similar to the RG ang AG that Dow chemicals use in their catalogues: RG being "reagent grade" (everyday lab chemicals) and AG being "analytical grade" (extra pure for special work).

The sg number is the Specific Gravity of the acid in question. Specific gravity is a nifty way of measuring the concentration / purity of an acid:

You can see in the product description that the acid on offer is 32%: 32 parts acid to 68 parts water.

Now if you had 100ml of  pure water, it would weigh 100g. However, 100ml of acid would weigh more than 100g, because of the acid content.

The sg 1.16 tells you that any volume of this acid will weigh 1.16 times more than the same volume of pure water. Obviously, if the acid was more concentrated, it would have a higher sg figure.

As UNIVAR is a chemical company, I suspect that this acid was made by them and sold on to this company, so the original source company is mentioned in the product description.

Hope this helps: if you can give me the name of the company, I'll happily try and find out a bit more about the initials.

Thanks very much again for your question.