protoxides

To deoxidation of the coloring matter by substances, which have a great tendency to become oxidised or peroxised; _e. g._ hydrogen, in the case of decolorisation by sulphuretted hydrogen, nascent hydrogen, and the protoxides of iron and tin, &c.

The Commercial Products of the Vegetable Kingdom Considered in Their Various Uses to Man and in Their Relation to the Arts and Manufactures; Forming a Practical Treatise & Handbook of Reference for the Colonist, Manufacturer, Merchant, and Consumer, on the Cultivation, Preparation for Shipment, and Commercial Value, &c. of the Various Substances Obtained From Trees and Plants, Entering into the Husbandry of Tropical and Sub-tropical Regions, &c. P. L. Simmonds

The protoxides -- including under that head the alkalies, earths, etc. -- are, as a class, the most stable compounds we know: most of them resisting decomposition by any heat we can generate.

Essays on Education and Kindred Subjects Everyman's Library Herbert Spencer 1861

The chlorides of potassium, sodium, barium, &c., are in the same relation to the protoxides of the same metals and present the same results under the influence of the electric current (402.).

Experimental Researches in Electricity, Volume 1 Michael Faraday 1829