AGRICULTURAL CHEMISTRY — AGROTECHNY. 203 



distilled water. Filter into a weighed 200 cc. Erlenmeyer flask, wash the residue 

 three or four times with hot water, replace the filter paper with residue in the 

 platinum dish, dry, and ignite until practically all the carbon is consumed. 

 Transfer the remaining ash to the Erlenmeyer flask with hot water, using a 

 policeman to loosen any particles that may adhere to the dish. Evaporate the 

 moisture and dry the ash at 110° C. until thoroughly dry ; weigh. The weight 

 minus the weight of the flask represents the crude ash. 



"Connect the flask containing the crude ash to an apparatus [described else- 

 where "] for determining the carbon dioxid, treat the contents of the flask with 

 80 cc. of distilletl water free from carbonates and 20 cc. of dilute hydrochloric 

 acid (1:10). Aspirate purified air through the apparatus while liberating the 

 carbon dioxid. Boil for 30 minutes and absorb the gas in 50 cc. of a 4 per cent 

 solution of sodium hydroxid. Drain the sodium hydroxid solution out of the ab- 

 sorption tower and wash the remaining caustic solution out of the tower with 

 250 cc. of CO^-free water. Exactly neutralize with normal hydrochloric acid, 

 using phenolphthalein as indicator. Add 2 drops of methyl orange solution (1 

 gm. in 1,000 cc.) and titrate with twentieth-normal hydrochloric acid until the 

 color of the methyl orange is just changed. From the number of cubic centi- 

 meters of twentieth-normal hydrochloric acid used subtract blank: 1 cc. 

 twentieth-normal hydrochloric acid=0.0022 gm. carbon dioxid. The titration 

 where phenolphthalein is used is ignored. The carbon, sand, and silica are 

 determined as outlined on page 22 in Bulletin 107, U. S. Bureau of Chemistry 

 [E. S. R., 20, p. 512]. The carbon dioxid plus the unburned carbon and sand is 

 subtracted from the weight of crude ash. The remainder represents the amount 

 of carbon-free ash." 



A Kjeldahl distillation apparatus, J. M. Pickel {Jour. Indus, mid Engin. 

 Chem., 7 (1915), No. 9, pp. 787-789, figs. 3).— An apparatus, which the author 

 states he has used for a number of years with excellent results, is described. 

 Claims are made that it is simpler, more flexible, and less costly than that de- 

 scribed by Holmes (E. S. R., 33, p. 10). 



Titration of nitrates with, ferrous sulphate, F. C. BoWman and W. W. 

 Scott {Jour. Indus, and Engin. Chem., 7 {1915), No. 9, pp. 766-769). — A simple 

 and reliable method for the titration of nitrates, as shown by analytical data 

 submitted, was devised by the authors. The method is based on the well-known 

 ferrous sulphate test for nitrates. The procedure recommended is as follows : 



Dissolve 176.5 gm. of ferrous sulphate heptahydrate in 400 cc. water, and stir 

 into tills gradually 500 cc. of dilute sulphuric acid 1 : 1. Cool the mixture and 

 make up to 1,000 cc. The order of mixing given should be followed, for a 

 different order is apt to cause precipitation of an iron sulphate that can not be 

 redissolved. 



Either potassium bichromate or nitric acid may serve for a standard. With 

 the former, the strength of the iron solution is estimated by Penny's method, 

 0.2 cc. being allowed for the end point in titrating nitrates. 



" A more satisfactory method of standardizing is to titrate a nitric acid solu- 

 tion of known strength under the exact conditions in which the iron solution is 

 to be used. For this, dilute 41 cc. of the usual 70 per cent laboratory nitric acid 

 to 1,000 cc. and titrate with normal caustic alkali. Use 10 cc. of the dilute 

 nitric acid to standardize the ferrous sulphate solution in the manner described 

 above." 



For titration the sample should be chosen to contain 0.3 to 0.6 gm. of nitric 

 acid. For the most accurate work, the titration should be on practically the 

 same quantity of nitric acid as was used in standardizing the solution. 



"Jour. Indus, and Engin. Chem., 4 (1912), No. 8, p. 611. 



