_Nitrous ether_, or _ethyl nitrite_, C_{2}H_{5}.ONO.--In a pure state this ether is best prepared according to the method given by E. Kopp. It consists in bringing equal volumes of alcohol and ordinary nitric acid together with copper filings into a distilling apparatus, which is so arranged that the vapors first pass through a flask filled with water of 77° F., then through a calcium chloride tube, and are finally condensed in a receiver surrounded by snow and common salt. The nitric acid is first decomposed by the copper, nitrous acid being thereby developed, which is so transposed that its radicle NO occupies the position of the typical hydrogen in the alcohol, while the rest of the acid forms water with the hydrogen of the alcohol. By the reaction such a quantity of heat is liberated that the process requires assistance by external heating only towards the end of the operation. In the receiver is then a pale yellow fluid having the taste and odor of apples and, at 59° F., a specific gravity of 0.947. According to Liebig, the boiling point of nitrous ether lies at 61.5° F.; hence it can be condensed only by careful cooling, and has to be kept in glass tubes fused together. In water it is but sparingly soluble, but readily so in alcohol. By the addition of water it is separated from the alcoholic solution. Mohr has modified Kopp's method as follows: Mix alcohol of 0.833 specific gravity, water, and nitric acid of 1.200 specific gravity, each 24 parts and add 4 parts of copper filings. Of this mixture draw off 24 parts of distillate, mix the latter with litmus tincture and neutralize the free acid by adding, drop by drop, solution of caustic potash or soda until the litmus tincture becomes blue. Rectify the distillate and catch of it 8 parts. Compound the latter with 16 parts alcohol of 0.833 specific gravity, whereby the product is made equal to the quantity of alcohol originally used. The product is kept in glasses holding from 2 to 3 ozs. each. This alcoholic nitrous ether is of a yellow color, very strong and has a pure odor. In England and America, nitrous ether is much used for aromatizing whiskies and for other purposes. According to Stinde[9] it is prepared on a large scale as follows:-- A stone-ware flask of at least 120 lbs. capacity, such as is used for the preparation of chlorine, is so placed upon a tripod in a sheet-iron cylinder that the neck projects over the edge of the cylinder. The space between the flask and the walls of the cylinder is completely filled with mats or coarse pack-cloth. A steam-pipe enters the lower part of the cylinder, while a cock placed on the bottom of the cylinder serves for discharging the condensed water. The cylinder is closed by a sheet-iron cover provided in the centre with a hole through which passes the neck of the flask. The flask is filled with 60 lbs of 90 per cent. alcohol free from fusel oil, to which, in small portions, 15 lbs. of crude nitric acid of 36° Bé. are added.