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Graham, Thomas

(Encyclopedia)Graham, Thomas, 1805–69, Scottish chemist, best known for research in diffusion in both gases and liquids that led to his formulation of Graham's law. His discovery that certain substances (e.g., gl...

acetate

(Encyclopedia)acetate ăsˈĭtātˌ [key], one of the most important forms of artificial cellulose-based fibers; the ester of acetic acid. The first patents for the production of fibers from cellulose acetate appea...

Bloch, Konrad Emil

(Encyclopedia)Bloch, Konrad Emil, 1912–2000, American biochemist, b. Neisse, Germany (now Nysa, Poland). He became a U.S. citizen in 1944. Bloch was educated at Munich and at Columbia (Ph.D., 1938). He taught at ...

umkokola

(Encyclopedia)umkokola, small, thorny S and E African tree (Dovyalis caffra, also called kei-apple), widely cultivated in its native area for the round or oval bright yellow fruits. Their juicy pulp, acid in flavor...

silica gel

(Encyclopedia)silica gel, chemical compound. It is a colloidal form of silica, and usually resembles coarse white sand. It may be prepared by partial dehydration of metasilicic acid, H2SiO3. Because it has many tin...

Richet, Charles Robert

(Encyclopedia)Richet, Charles Robert shärl rōbĕrˈ rēshāˈ [key], 1850–1935, French physiologist. From 1887 to 1927 he was professor at the Univ. of Paris. His special study was anaphylaxis, a term he used t...

petrochemical

(Encyclopedia)petrochemical, any one of a large group of chemicals derived from a component of petroleum or natural gas. The cracking processes for manufacturing gasoline produce vast quantities of gaseous hydrocar...

anemia

(Encyclopedia)anemia ənēˈmēə [key], condition in which the concentration of hemoglobin in the circulating blood is below normal. Such a condition is caused by a deficient number of erythrocytes (red blood cell...

autoimmune disease

(Encyclopedia)autoimmune disease, any of a number of abnormal conditions caused when the body produces antibodies to its own substances. In rheumatoid arthritis, a group of antibody molecules called collectively RF...

lead, chemical element

(Encyclopedia)lead, metallic chemical element; symbol Pb [Lat. plumbum]; at. no. 82; at. wt. 207.2; m.p. 327.502℃; b.p. about 1,740℃; sp. gr. 11.35 at 20℃; valence +2 or +4. One of the oldest metals used by h...