CONDUCT OF THE INCINERATION 51 



INCINERATION IN A MIXTURE OF SULFURIC AND 

 NITRIC ACIDS 



57. Destruction of Organic Matter. The preliminary destruc- 

 tion of the organic matter for the purpose of determining the 

 phosphoric acid and other mineral matters, save sulfur and nitro- 

 gen, may be conveniently conducted as follows : 



Neumann has proposed incineration in a mixture of sulfuric 

 and nitric acids as a convenient method of preventing the forma- 

 tion of free carbon, which is destroyed very slowly by subsequent 

 burning. 26 The acid mixture is prepared by pouring slowly 

 and with constant shaking, one-half liter of concentrated sul- 

 furic acid into one-half liter of concentrated nitric acid of a 

 specific gravity of 1.4. 



58. Apparatus. The incineration is carried on in a deep, round 

 flask of Jena glass which has the normal length of neck of about 

 10 centimeters and a capacity of from one-half to three-fourths 

 of a liter. Over this is placed in a glass or porcelain ring a funnel 

 provided with a stop-cock, which is conveniently provided with 

 a capillary dropping-tube, and the whole apparatus is fixed to an 

 appropriate stand. In the preparation of the sample different 

 processes are employed, according to the condition of the sam- 

 ple. Dry, powdery substances are placed in small glass tubes 

 (weighing tubes) which can be easily passed into the neck of the 

 incineration flask. Sticky substances can be placed in a piece of 

 a broken test-tube. Liquids can be placed in thin, weighed, small 

 tubes which are easily broken after placing in the flask. Dry or 

 moist substances can be used for the incineration, and even liquids 

 in not too large quantities, without any previous preparation. In 

 the case of blood it is better to evaporate it before incineration. 

 Fats or materials rich in carbohydrates, such as milk, should be 

 treated before incineration with one per cent, of pure potash lye 

 and evaporated to a sirupy consistence in order to avoid foaming 

 or bumping in the flask. For instance, for 25 cubic centimeters 

 of milk about 15 cubic centimeters of one per cent, potash lye 

 are used. 



59. Conduct of the Incineration. The substance which has been 

 16 Zeitschrift fur physiologische Chemie, 1902-3, 37 : 115- 



