Fike had a large write-up about this company. Some of the information is used here
Henry Pfeiffer started out as a druggist in Cedar Falls, SD. He later moved to St. Louis and with his brother Allan they started the Allan-Pfeiffer Chemical Co. They were in business under that name in St. Louis from 1891 until at least 1904. Apparently they weren't listed for a couple of years and then they were listed as the Pfeiffer Chemical Co. and they expanded to include offices in Philadelphia and New York (at different times). The Pfeiffer Chemical Co. was still in business in 1942.