II] SOILS 21 



purified by digestion with hj'drochloric acid and thorough washing with water. 

 The filter tube passes through a 1-holed rubber stopper which fits into a side arm 

 filtering flask. The side arm of this flask is connected to the suction pipe by a 2-way 

 stop-cock. In the top of the filter tube is fitted a 2-hoIcd rubber stopper carrying 

 glass tubes bent at right angles. To these tubes are attached rubber tubing bearing 

 pinch-cocks. One of these rubber tubes terminates in a tube containing soda lime. 

 The other rubber tube is connected with one end of the Meyer apparatus. The 

 other end of the Meyer apparatus is attached to a bottle containing carbon 

 dioxid-free water by means of a well-washed rubber tube and a glass tube extending 

 to the bottom of the bottle. This glass tube passes through a 2-holed rubber stop- 

 per. In the other hole of the stopper is placed a tube containing soda lime. A 

 pinch-cock is placed on the tube joining the water bottle and the Meyer apparatus. 

 This cock is kept closed until the precipitate on the filter is ready for washing. 

 With the pinch-cock on the air outlet of the filter tube closed and the pinch-cock 

 from the filter tube to the Meyer apparatus open, apply gentle suction to the 

 filter flask until the contents of the Meyer apparatus have been transferred to the 

 filter. When necessary, the pinch-cock to the air inlet of the filter tube is opened 

 to admit air behind the liquid in the Meyer apparatus. Open the pinch-cock be- 

 tween the wash-water bottle and the Meyer apparatus and open the stop-cock lead- 

 ing from the filter flask so as to maintain a gentle suction. By manipulation of 

 the Meyer apparatus the wash water comes in contact with all parts of the interior 

 of the apparatus, after which the water is sucked through the filter. After this 

 thorough washing admit air through the side opening of the stop-cock leading to the 

 filter flask. 



Disconnect the apparatus, remove the filter pad with the barium carbonate from 

 the filter tube by means of a glass rod, place in a beaker and add a measured amount 

 of N/10 hydrochloric acid in excess, first rinsing the Meyer bulbs with a small amount, 

 carefully measured, of this acid and water. Titrate the excess of acid with N/10 

 sodium hydroxid, using methyl orange as indicator. Make a blank determination 

 under the same conditions and apply the necessary correction. From the amount of 

 N/10 hydrochloric acid required to neutralize the barium carbonate formed by the 

 carbon dioxid in the sample, calculate the quantity of inorganic carbon. One cc. of 

 N/10 acid corresponds to 0.0006 gram of carbon. 



10 TOTAL NITROGEN.— OFFICIAL. 



Place 7-14 grams of the soil, as prepared under 2, in a 300 cc. Kjeldahl digestion 

 flask with 30 cc, or more if necessary, of concentrated sulphuric acid and 0.7 gram of 

 mercuric oxid, or 0.65 gram of mercury. Mix immediately by shaking to prevent the 

 soil from adhering to the sides of the flask. Heat over a low flame, increase the heat 

 gradually, and rotate the flask frequently or shake if necessary to prevent the con- 

 tents from sticking to the bottom of the flask. When all the organic matter is de- 

 stroyed, continue the digestion for 1 hour. Oxidize the residue with potassium 

 permanganate, carefully adding small portions at a time to the hot liquid until, after 

 shaking, the liquid remains green or purple. After cooling, dilute the contents of 

 the flask with 100 cc. of water and transfer to a 700 cc. copper flask, using about 150 cc. 

 of water to wash out the digestion flask. Add an excess of strong alkali solution 

 containing potassium sulphid, connect the flask with a distilling apparatus, mix the 

 contents thoroughly and complete the determination as directed in I, 18. 



