PROTOXIDE OF NITROGEN.

155

mucus, urea, uric acid, &c. It is found in the swimming bladders offishes.

Preparation. —The readiest method of procuring nitrogen is to burna piece of phosphorus in a confined portion of atmospheric air. Thephosphorus combines with the oxygen of the air and forms mctaphospho-ric acid. The residual gas after being thoroughly washed is nearly purenitrogen.

Properties.— It is a colourless, odourless, tasteless gas; neither com-

- bustible nor a supporter of combustion. It neither reddens

Nitrw- litmus, nor whitens lime water. Its sp. gr. is 0‘9722. It is

= u"' very slightly absorbed by water. Its equivalent by weight is 14,- by volume 1.

Characteristics. —Nitrogen is usually distinguished by its negativeproperties just described. The only positive test for it is combining itwith oxygen to form nitric acid. This may be effected in two ways ;either by electrifying a mixture of nitrogen and oxygen, or by burninga stream of hydrogen in a mixture of oxygen and nitrogen. The nitricacid thus produced reddens litmus, and when absorbed by potash may berecognised by the tests hereafter to be mentioned. (See Nitric Acid .)

Physiological effects. —The effects of nitrogen gas on vegetablesand animals are analogous to those of hydrogen before mentioned(p. 126). Thus, when inspired, it acts as an asphyxiating agent, by ex-cluding oxygen ; when injected into the blood it acts mechanically only.It is an essential constituent of the air employed in respiration.

Uses. —It has been mixed with atmospheric air, and inspired in cer-tain pulmonary affections, with the view of diminishing the stimulantinfluence of the oxygen, and thereby of acting as a sedative. {Bid. Mat.Med.)

Nitroge'nii Protox'ydum.—Protoxide of Ni'trogen.

History and Synonymes. —This gas was discovered by Dr. Priestleyin 1776. He termed it dephlogisticated nitrous air. Sir H. Davy , inhis “■Researches''' on it, calls it nitrous oxide. Its common name islaughing gas.

Natural History.— This compound is always an artificial pro-duction.

Preparation. —It is obtained by heating nitrate of ammonia in aglass retort. Every equivalent or 71 parts of the salt are resolved intothree equivalents or 27 parts of water, and two equivalents or 44 parts ofprotoxide.

INGREDIENTS USED.

Nitr c . A d .54

1 eq. NitrateAmm. 71

^leq.I

1 eq. Amm. . 17

• 1 eq. Nitr. 14•2 eq. Oxyg. 163 eq. Oxyg. 241 eq. Nitr. 143 eq. Hydr. 3

PRODUCTS.

2 eq. Protox. Nitr. 44

3 eq. Water ... 27

Properties. —At ordinary temperatures and pressure it is a colourlessgas, with a faint not disagreeable odour, and a sweetish taste. It is notcombustible, but is a powerful supporter of combustion, almost rivallingin this respect oxygen gas. Protoxide of nitrogen does not affect vege-table colours. It undergoes no change of colour or of volume whenmixed with either oxygen or the binoxide of nitrogen.