"Test the drain cleaner/sulfuric acid by weighing 500 cc. Drain cleaner/sulfuric acid is a heavy dark liquid and 500 cc should weigh between 917 and 920 grams. If 500 cc weighs substantially less than 917g, then it has been diluted with water and cannot be used. Look for a different brand of drain cleaner or obtain commercial-grade sulfuric acid, a non-watched chemical. The specific gravity of sulfuric acid is 1.84. 1000cc weighs 1840g. 500cc weighs 920g."
https://www.thevespiary.org/rhodium/Rhodium/chemistry/hclgas.argox.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/hclgas.argox.html)