SPIRIT OF NITROUS ETHER. 157 



Summary. 



In conclusion emphasis should be given to four points which 

 may be summarized as follows : 



1. When Sweet Spirit of Nitre is made from concentrated 

 nitrous ether the product should be shaken for several minutes 

 to insure thorough uniformity. 



2. A sample of Sweet Spirit of Nitre kept strictly in ac- 

 cord with Pharmacopoeia directions remained constant in 

 strength for 60 days and deteriorated but slightly during the 

 next 30 days. Under unfavorable conditions decomposition of 

 samples began at once and steadily continued. 



3. The Modified Method of analysis, as described in detail, 

 gives more accurate results than either the old or the new 

 Pharmacopoeia methods, and compared with the latter is more ' 

 economical in time and reagents and is easier of manipulation, 

 with less chance for error. For a quick method when extreme 

 accuracy is not required the old U. S. P. method (1890) gives 

 approximately correct results. 



4. When determining the ethyl nitrite in sweet spirit of 

 nitre by the liberation of nitrogen dioxide the volume of gas 

 does not become constant in "from thirty to sixty minutes" as 

 published directions would lead one to- suppose, but increases 

 slowly, and at a varying rate, which is influenced by numerous 

 different conditions, sometimes at least, for several days. For 

 this reason it is not practicable to attempt to obtain an abso- 

 lutely constant volume, nor to apply a factor to correct for these 

 last traces of gas, and a one hour period for the reaction to take 

 place, with frequent shaking, may be used with practically 

 correct results. 



