What is "insoluble phosphoric acid"

Phosphoric \Phos*phor"ic\, a. [Cf. F. phosphorique.]

1. (Chem.) Of or pertaining to phosphorus; resembling, or containing, from us; specifically, designating those compounds in which phosphorus has a higher valence as contrasted with the phosphorous compounds.

2. Phosphorescent. ``A phosphoric sea.'' --Byron. Glacial phosphoric acid. (Chem.)

   1. Metaphosphoric acid in the form of glassy semitransparent masses or sticks.

   2. Pure normal phosphoric acid.

      Phosphoric acid (Chem.), a white crystalline substance, H3PO4, which is the most highly oxidized acid of phosphorus, and forms an important and extensive series of compounds, viz., the phosphates.

      Soluble phosphoric acid, Insoluble phosphoric acid (Agric. Chem.), phosphoric acid combined in acid salts, or in neutral or basic salts, which are respectively soluble and insoluble in water or in plant juices.

      Reverted phosphoric acid (Agric. Chem.), phosphoric acid changed from acid (soluble) salts back to neutral or basic (insoluble) salts.