150 MAINE AGRICUI.TURAL EXPERIMENT STATION. I912. 



shortly afterwards found that an analysis made immediately 

 following the preparation of the sample might not give correct 

 results unless unusual care had been observed in the mixing. 

 This is a point of importance to the pharmacist as it indicates 

 that the concentrated nitrous ether mixes but slowly with 

 alcohol unless it is very thoroughly shaken. 



Methods oe Analysis. 



Three different methods of assaying spirit of nitrous ether 

 have been proposed : that given in the seventh revision of the 

 United States Pharmacopoeia, that given in the eighth revi- 

 sion of the same publication, and a modification or combination 

 of the two which may be found outlined in Schimpf's Manuel 

 of Volumetric Analysis.'^ These methods as given are as 

 follows : 



AfetJiod of Assay According to Seventh Revision of the U. 

 S. P. i8go. "If 5 Cc. of recently prepared Spirit of Nitrous 

 Ether be introduced into a nitrometer, and followed, first, by 

 10 Cc. of potassium iodide T. S., and then by 10 Cc. of normal 

 sulphuric acid, the volume of nitrogen dioxide generated at 

 the ordinary indoor temperature (assumed to be at or near 

 25° C, or '/y° F.) should not be less than 55 Cc. (correspond- 

 ing to about 4 per cent of pure ethyl nitrite)." 



Method of Assay According to the Eighth Revision of the 

 U. S. p. 1900. "Transfer about 30 Gm. of the Spirit of Nitrous 

 Etlter, which has been previously shaken with 0.5 Gm. of potas- 

 sium bicarbonate, to a tared 100 Cc. measuring flask, and weigh 

 it accurate^. Add sufficient alcohol to bring the volume to 

 exactly 100 Cc, and mix thoroughly. Introduce into a nitro- 

 meter (see Appendix, Gasometric Estimations) exactly 10 Cc. 

 of the alcoholic solution, followed by 10 Cc. of potassium iodide 

 T. S., and afterwards by 10 Cc. of normal sulphuric acid V. S. 

 When the volume of gas has become constant (within 30 to 

 60 minutes), note the volume of gas collected. Multiply this 

 volume in Cc. by 0.307, and divide the product by the original 

 weight of the Spirit of Nitrous Ether. At standard tempera- 

 ture and pressure the quotient will represent the percentage of 



* Fifth Edition, p. 683. 



