The use of a two-stage sulfuric acid hydrolysis for the analysis of lignin dates to the turn of the 20th century, although the use of concentrated acid to release sugars from wood dates to the early 19th century (7 ). Klason, in 1906, is often credited as the first to use sulfuric acid to isolate lignin from wood (7 −9 ). The method became named after Klason, and the insoluble residue from the test is known as “Klason lignin.” An English translation of a Klason paper, from this period (10 ), describes his attempt to determine the structure of spruce wood lignin. According to Brauns (7 ), Klason’s method originally used 72 wt % sulfuric acid; he later reduced this to 66 wt % to gelatinize the wood. He filtered the solids and subjected them to a second hydrolysis in 0.5 wt % hydrochloric acid.
Although Klason is generally credited as being the first to use sulfuric acid for lignin analysis, Sherrard and Harris (11 ) credit the use of sulfuric acid to Fleschsig in 1883, Ost and Wilkening in 1912, and König and Rump in 1913. According to Harris (12 ), Fleschsig, in 1883, dissolved cotton cellulose and converted it nearly quantitatively into sugars using strong sulfuric acid followed by dilution and heating. According to Browning (13 ), Ost and Wilkening introduced the use of 72 wt % sulfuric acid for lignin determinations in 1910. A translated paper by Heuser (14 ) credited König and Ost and Wilkening for the sulfuric acid lignin method. Dore (15 ) described several improved analytical methods (cellulose, lignin, soluble pentosans, mannan, and galactan) for the summative analysis of coniferous woods. The discrepancies in attribution may be due to differing definitions for the method cited (e.g., first to use acid to determine lignin, first to use sulfuric acid, first to use 72 wt % sulfuric acid, etc.) and to missed citations across continental distances in the early 20th century.