Barbo Compound was made by the Barbo Manufacturing Co. in New York City and was sold until at least 1955. The ad pictured above dates from 1917.
A 1942 report by the Connecticut Agricultural Experiment Station [link] describes Barbo Compound as a “pale yellow powder slightly acid to litmus” which is slightly alarming. Even more alarming: this statement in 1919 in the Michigan Food and Drug Monthly calling Barbo “poisonous” – it was roughly 1/3 lead acetate. “Little wonder…that in their circular they state specifically that they ‘assume no liability for the results of its use by anyone.”