CARBON IN ORGANIC SUBSTANCES BY THE KJELDAHL METHOD. 



755 



No. 1, . 

 » 2, 



0-3116 



,, o, 



0-3090 



,. 4, • 



0-3063 



Mean, 



0-3090 



Four samples of Loch Katrine water treated in same way. 



Organic Carbon. Organic Nitrogen. 



0-0240 

 0-0234 

 0-02272 

 0-02372 

 0-02346 



Percentage difference from mean of cases above and below mean. 



Carbon + 0'83 per cent. — 0'83 per cent. 

 Nitrogen + 1 -67 „ — 1*7 



Thus the mean working error in carbon is less than 2 per cent., and the mean working- 

 error in nitrogen is less than 3 per cent., when working with an amount of organic matter 

 yielding less than 2 milligrams of carbon and less than 0"2 milligram nitrogen. 



Effect of presence of nitrates on the estimation of nitrogen. 



The following experiments were made (in each experiment the samples were taken 

 from the same bottle of water) : — 



Experiment I. : — 



Edinburgh Main Water, 



Organic Organic 



Carbon. Nitrogen. 



0-3143 0-02354 



+ '98 grain nitrate of potassium per gallon, - 3116 0'02272 



Experiment II: — 



Edinburgh Main Water, 



. 



0-3116 



0-02450 



+ '98 grain nitrate of potassium per gallon, 



0-3143 



0-02450 



+ 1-47 



0-3143 



0-0232 



Experiment III.: — 



Edinburgh Main Water, 



+ '98 grain nitrate of potassium per gallon, 

 "T '"8 „ ,, ,, 

 + 1-47 

 + 1-47 



0-2928 

 0-2910 



0-0219 

 0-0212 

 0-0219 

 0-0182 

 0-01943 





0-2928 



Experiment IV.: — 



Edinburgh Main Water, 



0-3412 0-02223 



-r-1'98 grain nitrate of potassium per gallon, 0'3493 0'0206 



+ 1-98 „ „ „ 0-3412 0-01795 



The following shows the effect of the addition of ferrous sulphate as described :- 



