hydrurets

It is not so in the fields covered with indigo, or other herbaceous plants; where the rays of the sun penetrate freely into the earth, and by the accelerated combustion of the hydrurets of carbon and other acidifiable principles, destroy the germs of fecundity.

Travels to the Equinoctial Regions of America 1851

The reason that the earth is soon impoverished by the culture of indigo, particularly between the tropics, is because the rays of the sun penetrate freely into the earth, and by accelerated combustion of the hydrurets of carbon, and other accidified principles, destroy the germ of fecundity.

Documenting the American South: The Southern Experience in 19-th Century America 1844

It is not so in the fields covered with indigo, or other herbaceous plants; where the rays of the sun penetrate freely into the earth, and by the accelerated combustion of the hydrurets of carbon and other acidifiable principles, destroy the germs of fecundity.

Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804 — Volume 2 Alexander von Humboldt 1814