154 MAINK AGRICULTURAL LXPE^RIME^NT STATION. I912. 



When the assay is carefully made by this method every 

 trace of the weighed sample is used and there is no chance for 

 the escape of gas. That the result is m.ore accurate than that 

 obtained by the U. S. P. method of 1890 is evident from the 

 fact that the sample is accurately weighed. Different samples 

 vary in specific gravity as shown in Table 26 and, therefore, 

 if volume alone is considered, as in the old U. S. P. method, 

 the result can not be absolutely correct unless by accident. It 

 is of interest to compare the percentage of ethyl nitrite found 

 when the weight obtained by difference, as above, is used as a 

 basis and when the weight is calculated from the specific 

 gravity. 



In the 19 results thus compared in Table 26 three are alike, 

 the greatest difference is 0.04 per cent, and the average differ- 

 ence is only 0.02 per cent. 



If the modified method is more accurate than the old U. S. P. 

 method a study of Table 26 will show that it is more accurate 

 than the new U. S. P. method, of 1900, as this gives the lowest 

 average results of either of the three. Compared with the old 

 U. S. P. method the modified method gives results ranging 

 higher from 0.03 per cent to 0.25 per cent. Compared with the 

 new U. S. P. the modified method gives results ranging higher 

 from 0.05 per cent to 0.47 per cent. Comparing the old ani^ 

 new U. S. P. methods it is found that in twenty cases the old 

 method gives the highest results, the difi:erences running .from 

 0.02 per cent tO' 0.32 per cent ; while in three cases the new 

 method gives the highest, running however only from o.oi per 

 cent to 0.06 per cent. 



The modified method gives luiiform results when tried 

 several times upon the same sample, while among the results 

 obtained by the new U. S. P. method will often be found 

 variations similar to that noted in Table 26 under sample 

 number 10568, A and B. Compared with the new U. S. P. 

 method the modified method is less expensive in both time and 

 chemicals. In eliminating the shaking out with potassium 

 bicarbonate no error is introduced because if absolute accuracy 

 is required any free acid present may be washed into the nitro- 

 meter with alcohol before it comes in contact with any reagent; 

 while on the other hand the process is simplified thus reducing 

 the chance for error or loss. That the use of potassium bicar- 



