NITROUS OXIDE AS AN ANAESTHETIC. 
21 
favour, for it was discovered in 1776 by Priestley, and in 1800 Sir H. Davy care¬ 
fully examined the stimulating effects produced by its inhalation. The results 
obtained from these experiments gave to it the popular name of “ laughing gas.” 
Dr. Colton, who has been using the gas in America and in Paris, is in Eng¬ 
land at the present time, and may be considered as having had the largest expe¬ 
rience of this agent. He brings with him a register of some 27,000 cases 
where the gas has been used as a substitute for chloroform. 
When the nitrous oxide gas is inhaled through an ordinary chloroform inhaler, 
the effect is to produce anaesthesia ; in other words, if you want to obtain insen¬ 
sibility without excitement, the nitrous oxide must be given unmixed with air. 
The excitement produced by this gas, which has given it the name of laughing 
gas, is probably due to admixture of .carbonic acid and air exhaled from the 
lungs, for Sir H. Davy’s experiments seem to have been made with gas which 
was placed in a silk bag, and this gas was allowed to be breathed backwards and 
forwards into the bag. 
Protoxide of nitrogen, or nitrous oxide, called by Priestley dephlogisticated 
air, is made by heating pure nitrate of ammonia in a flask to a temperature of 
350° Fahr., when it puts on the appearance of ebullition, and is entirely decom¬ 
posed into nitrous oxide and water,— 
NH 4 0,N0 5 =4H0+2N0; or, NH 4 N0 3 ==2H 2 0+:Nr 3 0. 
The gas should be collected over water, but cold water dissolves it to the ex¬ 
tent of one volume, therefore warm water, in which it is less soluble, is fre¬ 
quently used in the pneumatic trough. If considerable quantities are to be col¬ 
lected, the same water should be returned to the gas-holder from time to time ; 
it thus becomes saturated with the gas, and may then be used without being 
warmed. 
In making the gas there are several precautions necessary. The nitrate of 
ammonia must be pure ; if it contain chloride of ammonium or sulphate of am¬ 
monia the gas will be impure. If too great a heat be applied, there will be a 
complex decomposition, with production of some of the higher oxides of nitrogen. 
On the other hand, at a temperature a little below that at which the gas is pro¬ 
duced, the nitrate of ammonia itself is sublimed, either with or without decom¬ 
position. 
The following effects of the application of heat to nitrate of ammonia were 
observed and recorded by Sir H. Davy :— 
1. Dry nitrate of ammonia undergoes little or no change below 260° F. 
2. When heated to between 270° and 300°, it slowly sublimes without decom¬ 
position and without becoming fluid. 
3. At 320°, it liquefies, decomposes, and still slowly sublimes. It never as¬ 
sumes nor continues in the fluid state without undergoing decomposition. 
4. At temperatures between 340° and 480°, it decomposes rapidly, yielding 
pure nitrous oxide and water, as shown above. 
5. If heated to 600° and above, the decomposition is accompanied by a lumi¬ 
nous appearance of the salt, and nitric oxide, nitrous acid, and nitrogen are 
evolved. 
In collecting the gas, when it is intended to be used for inhalation, it is desi¬ 
rable to pass it through solution of sulphate of iron and solution of potash or soda 
contained in separate Woulfe’s bottles, before conveying it into the gas-holder. 
It would thus be purified from any of the higher oxides of nitrogen or other gas 
likely to be injurious that might be generated in the process. 
Pure nitrate of ammonia can be easily procured; if not, it is readily made by 
saturating carbonate of ammonia with pure nitric acid, and crystallizing. 
One ounce of nitrate of ammonia yields about 500 cubic inches (nearly two 
gallons) of gas. 
Nitrous oxide has been condensed into the liquid state by mechanical pressure. 
