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A genus of diatoms of elongated elliptical shape, but having the sides slightly curved in the form of a letter S. Pleurosigma angulatum has very fine striations, and is a favorite object for testing the high powers of microscopes.

combining form or prefix from Gr. poly`s, many; as, polygon, a figure of many angles; polyatomic, having many atoms; polychord, polyconic.

r of combining with, several molecules of a monobasic acid; having more than one hydrogen atom capable of being replaced by acid radicals; -- said of certain bases; as, calcium hydrate and glycerin are polyacid bases.

izing, or of combining with, several molecules of a monacid base; having several hydrogen atoms capable of being replaced by basic radicals; -- said of certain acids; as, sulphuric acid is polybasic.

A bromide containing more than one atom of bromine in the molecule.

A chloride containing more than one atom of chlorine in the molecule.

gnating, any one of several acids (known only in their salts) which contain more than one atom of chromium.

A iodide having more than one atom of iodine in the molecule.

n of; to produce polymers from; to increase the molecular weight of, without changing the atomic proportions; thus, certain acids polymerize aldehyde.

A sulphide having more than one atom of sulphur in the molecule; -- contrasted with monosulphide.

Containing several tungsten atoms or radicals; as, polytungstic acid. Polytungstic acid (Chem.), any one of several complex acids of tungsten containing more than one atom of tungsten.

At or toward the caudal extremity; caudal; -- in human anatomy often used for dorsal.

Existing or living after. [R.] "Postexistent atoms." Cudworth.

te, carbonate, or silicate, in the minerals sylvite, kainite, orthoclase, muscovite, etc. Atomic weight 39.0. Symbol K (Kalium).

the constituents of didymium; - - so called from the green color of its salts. Symbol Ps. Atomic weight 143.6.

oxidized so as to form a corresponding aldehyde and acid having the same number of carbon atoms; -- distinguished from secondary and tertiary alcohols. -- Primary amine (Chem.), an amine containing the amido group, or a derivative of ammonia in which only one atom of hydrogen has been replaced by a basic radical; -- d…

One who makes dissections for anatomical illustration; usually, the assistant of a professional anatomist.

Sometimes used as equivalent to mono-, as indicating that the compound has but one atom of the element to the name of which it is prefixed. Also used adjectively.

A silicate formed with the lowest proportion of silicic acid, or having but one atom of silicon in the molecule.

phides of any element which has the lowest proportion of sulphur; a sulphide with but one atom of sulphur in the molecule.