K

kainiteA naturally occurring dou-
ble salt of magnesium sulphate and
potassium chloride, MgSO 4 .KCl.3H 2 O.

kaliniteA mineral form of *alu-
minium potassium sulphate
(Al 2 (SO 4 ) 3 .K 2 SO 4 .24H 2 O).

kaolin(china clay)A soft white clay
that is composed chieÛy of the min-
eral kaolinite (see clay minerals). It is
formed during the weathering and
hydrothermal alteration of other
clays or feldspar. Kaolin is mined in
the UK, France, the Czech Republic,
and USA. Besides its vital importance
in the ceramics industry it is also
used extensively as aÜller in the
manufacture of rubber, paper, paint,
and textiles and as a constituent of
medicines.

Kastle Meyer test (phenolph-
thalein test)A presumptive test used
to indicate blood. Phenolphthalein
and hydrogen peroxide are used; re-
action with haemoglobin in the
blood gives a pink colour.

katharometer An instrument for
comparing the thermal conductivi-
ties of two gases by comparing the
rate of loss of heat from two heating
coils surrounded by the gases. The in-
strument can be used to detect the
presence of a small amount of an im-
purity in air and is also used as a de-
tector in gas chromatography.

Kekulé, Friedrich August von
Stradonitz(1829–96) German
chemist, who became professor at
Ghent (1858) and later at Bonn
(1867). He studied the structures of
organic molecules and was theÜrst
to recognise that carbon atoms form

stable chains. Kekulé is best remem-

bered for his proposed structure for

{benzene} in 1865, which he cor-

rectly interpreted as having a sym-

metrical ring of six carbon atoms.

Kekulé structure A proposed

structure of *benzene in which the

molecule has a hexagonal ring of car-

bon atoms linked by alternating dou-

ble and single bonds. Kekulé

structures contribute to the reso-

nance hybrid of benzene. The struc-

ture was suggested in 1865 by

Friedrich August *Kekulé.

kelvinSymbol K. The *SI unit of

thermodynamic *temperature equal

to the fraction 1/273.16 of the ther-

modynamic temperature of the

*triple point of water. The magni-

tude of the kelvin is equal to that of

the degree Celsius (centigrade), but a

temperature expressed in degrees

celsius is numerically equal to the

temperature in kelvins less 273.15

(i.e. °C = K – 273.15). The *absolute

zero of temperature has a tempera-

ture of 0 K (–273.15°C). The former

name degree kelvin (symbol °K) be-

came obsolete by international agree-

ment in 1967. The unit is named

after Lord Kelvin.

Kelvin, Lord (William Thomson;

1824–1907) British physicist, born in

Belfast, who became professor of

natural philosophy at Glasgow Uni-

versity in 1846. He carried out im-

portant experimental work on

electromagnetism, inventing the

mirror galvanometer and contribut-

ing to the development of telegra-

phy. He also worked with James

*Joule on the *Joule–Thomson (or