Dictionary of Chemistry [6th Ed.]

(kJ g–1), although Calories (kilocalo-

ries) are often still used in nontechni-

cal contexts. CaloriÜc values are

measured using a *bomb calorime-

ter.

calorimeterAny of various devices

used to measure thermal properties,

such as caloriÜc values or heats of

chemical reactions. See also bomb

calorimeter.

Calvin, Melvin(1911–97) US bio-

chemist. After World War II, at the

Lawrence Radiation Laboratory,

Berkeley, he investigated the light-in-

dependent reactions of *photosyn-

thesis. Using radioactive carbon-14 to

label carbon dioxide he discovered

the *Calvin cycle, for which he was

awarded the 1961 Nobel Prize for

chemistry.

Calvin cycleThe metabolic path-

way of the light-independent stage of

*photosynthesis, which occurs in the

stroma of the chloroplasts. The path-

way was elucidated by Melvin

*Calvin and his co-workers and in-

volves theÜxation of carbon dioxide

and its subsequent reduction to car-

bohydrate. During the cycle, carbon

dioxide combines with *ribulose bis-

phosphate, through the mediation of

the enzyme ribulose bisphosphate

carboxylase, to form an unstable

six-carbon compound that breaks

down to form two molecules of the

three-carbon compound glycerate

3-phosphate. This is converted to

glyceraldehyde 3-phosphate, which is

used to regenerate ribulose bisphos-

phate and to produce glucose and

fructose.

calxA metal oxide formed by heat-

ing an ore in air.

camphorA white crystalline cyclic

ketone, C 10 H 16 O; r.d. 0.99; m.p.

179 °C; b.p. 204°C. It was formerly ob-

tained from the wood of the For-

mosan camphor tree, but can now be

synthesized. The compound has a

characteristic odour associated with

its use in mothballs. It is a plasticizer

in celluloid.

calorimeter 96

c
CHCHCH 333

HHH 333 C C CHC C CHC C CH 333

COCOCO

CCC

CHCHCH 222

CCC

HHH

HHH 222 CCC

HHH 222 CCC

Camphor

Canada balsamA yellow-tinted

resin used for mounting specimens

in optical microscopy. It has similar

optical properties to glass.

candelaSymbol Cd. The *SI unit of

luminous intensity equal to the lumi-

nous intensity in a given direction of

a source that emits monochromatic

radiation of frequency 540 × 1012 Hz

and has a radiant intensity in that di-

rection of 1/683 watt per steradian.

cane sugar See sucrose.

cannabinoidsA large group of

structurally related phenolic com-

pounds found in the plant Cannabis

sativa. The main one is *tetrahydro-

cannabinol (THC), which is the com-

pound responsible for the affects of

cannabis. It affects cannabinoid re-

ceptors found in the brain (and also

in the spleen). The name ‘cannabi-

noid’ is also applied to structurally

unrelated compounds found natu-

rally in animal tissue and having an

affect on the cannabinoid receptors.

These endocannabinoids(endog-

enous cannabinoids) are believed to

act as ‘messengers’ between cells.

cannabisAn illegal drug produced

from the plant Cannabis sativa. The

dried inÛorescences of the plant are

known as marijuanaand the thick

resin produced from the plant is