AGEICULTURA.L CHEMISTEY — AGEOTECHNY. 315 



to dryness of the citric-acid extract with hydrochloric acid, and (2) boiling the 

 extract with sulphuric and nitric acids. Tlie first method was found to be 

 preferable, but the manipulation was not easy and in inexperienced hands led to 

 erroneous results. It was later shown by other investigators that the silicic 

 acid was only precipitated when the slag was poor in soluble iron. Through 

 this soluble iron, which acted as a protective colloid, the silicon dioxid was 

 held in solution in the amnioniacal liquid. In the absence of soluble iron even 

 traces of silicic acid were found to be objectionable. 



In devising a new method salts of chromium, zinc, aluminum, nickel, cobalt, 

 copper, mercury, and lead were tried, but not found to prevent the precipitation 

 of the silicic acid. Ferric chlorid, ferric ammonium sulphate, ferrous ammonium 

 suliihate, ferric nitrate, ferric carbonate, potassium ferroeyanid, and potassium 

 ferricyanid were also tried, and it was found that only the presence of the iron 

 ion was necessary, the acid ion used having no effect on the desired result. The 

 outline of the improved citrate method follows : 



Five gm. of Thomas slag is treated in a half-liter Stohman flask with 5 cc. 

 of alcohol to prevent caking on the bottom of the flask. The flask is filled to the 

 mark at 17.5° C. with a 2 per cent solution of citric acid and shaken for one-half 

 hour in a mechanical shaker. The solution is then filtered, 50 cc. of the clear 

 filtrate treated with 25 cc. of the iron citrate solution, to which is added 1 cc. 

 of a 3 per cent solution of hydrogen peroxid and 25 cc. of magnesia mixture, the 

 liquid stii'red for one-half hour and the precipitate filtered, ignited, and weighed. 

 The author gives in detail the procedure for the preparation and testing of the 

 reagents necessary in working the method, and discusses the details and possible 

 soui'ces of error of the method. A table for converting grams of magnesium 

 pyrophosphate to percentages of phosphorus pentoxid is appended. 



Studies on the estimation of inorganic phosphorus in plant and animal 

 substances, E. B. Fokbes, F. M. Beegle, and A. F. D. Wussow (Ohio Sta. Tech. 

 Bui. S {JO Jo), pp. 5-4S).— As previously noted (E. S. R., 23, p. 303) the senior 

 author and associates outlined two different methods for the estimation of in- 

 organic phosphorus, one for use with plant products and the other for materials 

 of animal origin. The investigation on improvements of the methods has been 

 continued for a period of three years, and the results are here reported. 



The improved procedure for the determination of inorganic phosphorus in 

 vegetable substances is as follows : 



"Pour exactly 300 cc. of 0.2 per cent hydrochloric acid (4.6 cc. concentrated 

 hydrochloric acid, sp. gr. 1.18 to 1.19, per liter) onto 10 gm. of sample in a dry 

 400-cc. Florence flask. Close with rubber stopper and shake at intervals of 5 

 minutes for 3 hours. Filter the extract by suction into dry flasks through S. 

 and S. No. 5S9 ' Blue Ribbon ' papei's, in a Witt filtering apparatus, or a Biichner 

 funnel. 



" Measure out a 250-cc. portion of this filtered extract and precipitate in a 

 400-cc. beaker with 10 cc. magnesia mixture and 20 cc. ammonia, sp. gr. 0.9. 

 Allow to stand over night and filter through double S. and S. No. 589 ' White 

 Ribbon ' papers, taking care to decant as long as possible without pouring out 

 the precipitate. Then complete the transfer of the precipitate to the paper. 



" Wash three times with 2.5 per cent ammonia and then three times with 95 

 per cent alcohol. Allow the precipitate to drain, and then spread out the inner 

 paper on the top of the funnel, and allow the alcohol to evaporate. When prac- 

 tically dry place this inner paper with the precipitate into an Erlenmej'er flask. 

 Add 100 cc. of 95 per cent alcohol containing 0.2 per cent of nitric acid. Close 

 the flask with a rubber stopper and shake vigorously until the paper is thor- 

 oughly broken up. If the precipitate is flaky and refuses to break up on shak- 

 ing, allow to stand in the acid-alcohol over night. 



