62 
APPARATUS FOR PREPARING NITROUS OXIDE GAS. 
narrative, or to descriptive subjects, such as the reports of meetings, of dinners, 
of presentations, etc.; and to speeches, whether laudatory, retrospective, or 
merely post-prandial. Would the writer kindly instruct us, some of whom vvill 
probably become hereafter provincial secretaries, how we are to set about making 
“ precis ” of such subjects ? If he had any clear aim in writing his article, to 
convey this information should have been his aim. When any chain of reason¬ 
ing is involved, I think some of us might contrive to manage some kind of a 
u precis” even without two years’ training. But how to precis reports of pro¬ 
ceedings, of conventional speeches, or of descriptions of new chemicals, new pro¬ 
cesses, or new instruments, altogether surpasses our comprehension. 
If, for instance, Mr. luce will have the kindness,—and the task need not 
occupy him for more than an hour,—to oblige us with a “precis ” (which shall 
be neither an abstract nor an epitome) of the Edinburgh proceedings (pp. 19 to 
25 t July number), to serve at once as an example, and an illustration of his 
meaning, he will render a substantial service, alike to Provincial secretaries, to 
readers of the Journal, to its official Editors, and finally, even to himself; inas¬ 
much as he will then have extricated his article from the haze of unrealism, 
impracticality, and aimlessness in which it lies at present hopelessly enveloped. 
At this point, “ Hie labor!—hoc opus est!” comments my impetuous friend, 
and forthwith vanishes. I hope his quotation is pertinent; for, now that he 
has gone, I am sure I should not know where to look for a better one. 
APPARATUS POR PREPARING NITROUS OXIDE GAS. 
BY J. T. PORTER. 
Since the introduction to the medical profession of nitrous oxide gas as an 
anaesthetic for operations in dentistry, its administration has received consider¬ 
able attention from, surgeons and dentists, and has also occupied the study of phy¬ 
siologists. Many experiments have been made to effect an easy and safe process 
for its production in a pure state. It may scarcely be necessary to observe that 
although nitrous oxide can be produced by acting upon zinc with a mixture of 
dilute nitric and sulphuric acids, it may conveniently and is more commonly ob¬ 
tained in a purer state by heating nitrate of ammonia to a temperature of about 
400° Fahr., when the salt is decomposed into water, and a gas composed of two 
of nitrogen and one of oxygen combining to form two volumes of nitrous oxide 
(N.,0) or laughing gas. In this way it was discovered by Priestley in 1776. 
Its" properties and stimulating effects produced by its inhalation were fully in¬ 
vestigated by Sir H. Davy in 1800. However, I shall not give its history, as 
it has already appeared in this Journal, Vols. IX. and X., also in the Journal 
of the Transactions of the Odontological, Medico-Chirurgical, and other Socie¬ 
ties. The following is an account of an improved method of obtaining it in a 
pure state, together with a description of an apparatus contrived to regulate 
the heat in its preparation. 
From the first use of this gas in England for anaesthetic purposes, rather more 
than a year since, namely, April, 1868, it has been my duty almost daily to 
make large quantities of it for the dental and other hospitals, and unavoidably 
many accidents have occurred, resulting in devising as many improvements, 
both in manipulation and apparatus, to prevent their recurrence. Having at 
last arrived at a period when breakages arising from over-heat or pressure are 
rare, together with a greater reliance in the purity of the gas, I now bring 
