HYDROCARBON

This article appears in Volume V14, Page 112 of the Encyclopedia Britannica.

Encyclopedia Britannica - Main :: HOR-I25

HYDROCARBON , in

chemistry

, a compound of carbon and hydrogen. Many occur in nature in the free state: for example, natural gas, petroleum and paraffin are entirely composed of such bodies; other natural sources are india-rubber, turpentine and certain essential oils. They are also revealed by the spectroscope in stars, comets and the sun. Of artificial productions the most fruitful and important is provided by the destructive or dry

distillation

DISTILLATION (from the Lat. distillare, more correctly destillare, to drop or trickle down)

of many organic substances; familiar examples are the

distillation

DISTILLATION (from the Lat. distillare, more correctly destillare, to drop or trickle down)

of coal, which yield's

ordinary

ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

lighting gas, composed of gaseous hydrocarbons,'and also coal tat, which, on subsenuent fractional distillations, yields many `liquid and
C,H5N2Cl + K2SO, = KCI + C,H,N2SO3K,
C6H5N>SO3K + 2H = C,H,NHNHSO3K,C5H,N H NH SOsK+HCI + H2O = C6H, NH N H2' FICI + KHSO1.
Phenylhydrazine is a colourless oily liquid which`rturtis brown on exposure. It boils at 241 C., and melts at 17.5 C. It is slightly soluble in water, and is strongly basic, forming well-defined salts with
r u acids.
uch for For
ethe detection of xample as aldehydes and ketones) hc d az lie orbital plates of the frontal bone being inclined forwards give
a ~ very important reagent, since des it combines? with enthlhem with a downward' tilt to the eyes, which have also peculiar

rolling

ROLLING

elimination of water and the formation of well-defined hydrazones movements. The face is small, and this, with the enlarged head, gives 'a remarkable aged expression to the child. The

body

BODY

is ill-noilrished,, the bones are thin, the

hair

HAIR (a word common to Teutonic languages)

is scanty and fine and the teeth" carious or absent.
The

average

AVERAGE

circumference of the adult head'is 22 in., and in the normal child it is of course much less. In chronic hydrocephalus the had of an infant three months old has measured 29 in.; and in the case of the man Cardinal, who died` in Guy's

Hospital

;' the head 'Measured 33 in. In such cases the head cannbt be' supported by the neck, and the patient has to keep mostly in the recumbent posture. The expansibility of the skull prevents destructive pressure on the brain, yet this organ is materially affected by the presence of the fluid. The cerebral ventricles are distended, and the convolutions are flattened. Occasionally the fluid escapes into the cavity of the cranium, which it fills, pressing down the brain to the base of the skull. - As i. consequence, the functions of the brain are interfered with, and the mental

condition

CONDITION (Lat. condicio, from condicere, to agree upon, arrange; not connected with conditio, from condere, conditum, to put together)

is impaired. The child is dull, listless and irritable, and sometimes imbecile. The

special

SPECIAL

senses become affected as the disease advances; sight is often lost, as is also hearing. Hydrocephalic children generally sink in a few years; nevertheless there have been instances of persons with this disease living to old age. There are, of course, grades of the affection; and children may present many of the symptoms of it in "a slight degree, and yet recover, the head ceasing to expand, and 'becoming in due coirtse'firmly ossified.
Various methods of treatment have been employed, but the results are unsatisfactory. Compression of the head by bandages, and the administration of mercury with the view of promoting absorption of the fluid, are now little resorted to. Tapping the fluid from time to time through one of the spaces between the bones, drawing off a little, and thereafter employing gentle pressure, has been tried, but rarely with benefit. Attempts have also been made to establish a permanent drainage between the interior of the lateral ventricle and the sub-dural space, itnd between the lumbar region of the spine and the abdomen, but without satisfactory results. On the whole, the plan of treatment which aims at maintaining the patient's nutrition by appropriate food and tonics is the most rational and successful. (E. 0.')

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