III. PLANT CONSTITUENTS. 



1 PREPARATION OF SAMPLE.— OFFICIAL. 



Thoroughly cleanse the material from all foreign matter, especially from adhering 

 soil, air-dry, grind, and preserve the sample in tightly stoppered bottles. 



2 PREPARATION OF ASH.— OFFICIAL. 



Ignite 10-20 grams of the substance, in a fiat-bottomed platinum dish in a muffle, 

 at a comparatively low temperature. Do not employ a full red heat because of the 

 danger of volatilizing alkali chlorids, etc. If rich in silica and alkalies, char the 

 material, treat with water to dissolve soluble salts, filter through an ashless filter, 

 dry the filter and paper and incinerate, add the filtrate to the incinerated residue, 

 evaporate to dryness and ignite at a low red heat. If rich in phosphates, e.g., seeds 

 and animal substances, char the material, dissolve soluble salts in dilute acetic 

 acid, filter through an ashless filter, wash with water, dry and incinerate the filter 

 and residue, add the filtrates to the incinerated residue, evaporate to dryness, and 

 ignite gently. While still warm, pulverize the whole of the ash as obtained above, 

 mix intimately and preserve in a tightly stoppered, dry bottle. If after incineration 

 the ash has absorbed moisture, dry thoroughly at low redness before bottling. 



3 CARBON DIOXID.-OFFICIAL. 



Determine carbon dio.xid in a weighed portion of the ash prepared under 2. Lib- 

 erate the carbon dio.xid by treatment with dilute hydrochloric acid in any of the 

 usual forms of apparatus, and determine the increase in weight of the potash 

 bubs. The efficiency of the apparatus should be tested by blank determinations 

 conducted upon weighed portions of pure calcite. 



4 CARBON, SAND AND SILICA.— OFFICIAL. 



Transfer the residue from the carbon dioxid determination to a beaker or evapo- 

 rating dish; evaporate to dryness; pulverize and dry thoroughly to render the silica 

 insoluble. Moisten the dry residue with 5-10 cc. of hj'drochloric acid, add about 

 50 cc. of water, allow to stand on the water bath for a few minutes, filter through 

 a hardened filter and wash thoroughly. Dilute the solution and washings to 250 

 cc. or other convenient volume. Designate as .4. 



Wash the residue from the filter into a platinum dish and boil for about 5 minutes 

 with approximately 20 cc. of a saturated solution of pure sodium carbonate, add a 

 few drops of pure sodium hydroxid solution, allow the solution to settle and decant 

 through a tared Gooch filter. Boil the residue in the dish with sodium carbonate 

 solution and decant as before. Repeat the process again, then transfer the residue 

 to the Gooch filter, wash thoroughly, first with hot water, then with a little dilute 

 hydrochloric acid, and finally with hot water until free from cblorin. Dry the filter 

 and contents to constant weight at 110°C. to determine the combined weight of 

 carbonaceous material and sand. Incinerate; the loss in weight represents the 

 carbonaceous material; the residue is sand. Confirm by microscopic examination. 

 Determine the soluble silica as follows: (1) Combine the alkaline filtrate and wash- 

 ings, acidify with hydrochloric acid, evaporate to dryness and determine the silica 



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