91 



should have been obtained. As method (g) permits the use of magnesia only, no 

 soda, in distilling, it is evident how very inaccurately this method is practiced by 

 -nun- chemi.-is. It would seem that the magnesia distillation process is conducted 

 by many ehemi.-t.- !>.- .- uccessfully than any other analytical process. 



Furthermore, the work of Bailey and Morrison shows that by method (g) some 

 ammonia is obtained from cotton-seed meal, about 2 or 3 per cent of the total nitrogen 

 in the Mib.-tance coming off as ammonia, when the distillation is off magnesia, and 

 about three time.- as much in addition, when soda is used in the distillation. This is 

 fortunately a compensating error and contributes something toward making up the 

 deficit ju>t described due to distilling ammonia off magnesia. 



Afl practiced by some chemists the process of distilling off magnesia is worse than 

 u.-elc. . A.- method (g) does not affect the amount of total nitrogen, errors are not 

 MB, however, as in methods (c) and (d). 



Method . hi show.- better agreement among different chemists and also gives figures 

 somewhat approximating theory. 



The only report on method (f) is to the effect that excessive frothing prevented 

 distillation. 



Of the 54 answers to the 14 questions stated above, 39, or nearly three-fourths, must 

 iiMdered unfavorable, either as failing to reach the 98 per cent standard of 

 accuracy or us showing reactions contrary to the plan and purpose of the method. 



It iiiu.-i be admitted, whatever may be the inherent accuracy of the several methods 

 heir di.-cussed, that m<i of them in the hands of some experienced chemists fail to 

 i:ive reasonably reliable and accurate results. It must also be admitted that these 

 method- \\ith D a variation in detail are commonly accepted by chemists as 



reliable, and, a.- tin- report -how-, may be made to give exceptionally accurate results. 

 <)b\iou-l\ method- >o firmly established, and by some analysts so successfully em- 

 ployed, .ire hardly to be condemned, or even seriously questioned, without a study 

 of them by a large number of chemists. The data obtainable for this report are too 

 meager to justify any criticism or proposed radical change. 



Th- -t ill of the opinion that the methods here discussed are fairly accurate 



when properly followed, le-.- a < urate perhaps in the hands of some analysts than 



method- applied to -impler determinations, nuch as of nitrate-free nitrogen, but yet 



urate as the difficulty of the case permits; and furthermore, that unquestionably 



the.-.- methods are not always successfully followed, as evidenced by the criticisms 



of chemists as well as by the reported results, and that probably some analyses made 



:ding to these methods arc erroneous, giving too low results; that the complaint 



of the officers of the National 1-Vrtili/er Association may possibly be based on fact in 



n cases, probably due in part to erroneous analyses and in part to actual loss 



of nitric acid, but that it is not within the power of this association at present to remedy 



the e\ il complained of, if it exists. 



KM OMMENDATIOX8. 



Two recommendations of 1!M)7, referred to the referee for 1908, are recommended 

 ioption as ollicial. Nor-. _' and 4, Circular 38, page 1, or Bulletin 116, page 129.) 

 Th.-se changes relate to the use of copper sulphate in the Kjeldahl and Gunning 

 methods. For detailed statement of changes see page 183. 



Recommendation 3: Bulletin 107 Rev., page 8, fourth line from top, after the word 

 ''time " insert : "Allow the flask to stand without heat for not less than six hours." 



K> commendation 4: Same reference, page 8, under (d) (3) "determination," 

 fifth line of paragraph, after word "and" insert: "Allow the flask to stand without heat 

 for not !>.- than six hours; then". So changed the sentence beginning with "Add 

 i ins" would read: "Add 5 grams of sodium thiosulphate and allow the flask to 

 *und without heat for not less than six hours; then heat the solution for five minutes; 

 cool; add 10 grams," etc. 



