318 EXPERIMENT STATION RECORD. [Vol. 3G 



plete the distillate is made up to about 300 cc. volume, put under a reflux con- 

 denser, and boiled gently for 45 minutes. The precipitate is then filtered hot 

 through paper, washed by decantation twice with hot water, and dissolved in 

 two or three small portions of 5 per cent hydrochloric acid by heating. The 

 acid solution is, after cooling, neutralized with 10 per cent sodium hydroxid, 

 and made up to 100 cc. volume. 



The whole or an aliquot of the mercury solution can be titrated against 

 standard potassium iodid solution, or the mercuric chlorid solution can be 

 used in a burette and titrated against standard potassium iodid. A determi- 

 nation factor giving the citric acid equivalent of cubic centimeters of potassium 

 iodid is included. Malic, tartaric (except quantities of 5 gm. or over), oxalic, 

 and aconitic acids do not interfere with the determination. The presence of 

 large amounts of sugar or other substances capable of reducing permanganate 

 tends to yield slightly high results, but the difference is inconsiderable. 



Analytical data are submitted which indicate that the modified method, if 

 followed rigidly, will give much more satisfactory results than the original 

 procedure. 



A comparison of barbituric acid, thiobarbituric acid, and malonylguanidin 

 as quantitative precipitants for furfural, A. W. Dox and G. P. Plaisance 

 {Jonr. A7ner. Cliem. Soc, 38 (1916), No. 10, pp. 2i56-2J64)-— Experimental data 

 submitted by the authors from the Iowa Experiment Station demonstrate that 

 thiobarbituric acid condenses readily with furfural in 12 per cent hydrochloric 

 acid solution, and forms, by the elimination of one molecule of water, a definite 

 compound to which a definite chemical formula can be ascribed. The reaction 

 is quantitative, yielding a voluminous precipitate which can be filtered, dried, 

 and weighed, Thiobarbituric acid is indicated as being superior to phloro- 

 glucinol as a precipitant for furfural, and no correction for solubility of the 

 product is necessary. It is also preferable to barbituric acid, for the reason 

 that the reaction is quantitative with as small amounts of furfural as 12 mg„ 

 and a large excess of percipitant is unnecassary, thus avoiding possible errors 

 due to inclusion. The precipitant has a further advantage in that the per- 

 centages of nitrogen and sulphur can be easily determined in cases where 

 doubt might exist as to the purity of the product in case homologues of fur- 

 fural were present. 



It is suggested that thiobarbituric acid, which can be prepared in a pure 

 state with little difficulty, may be found useful in the analysis of agricultural 

 products. In place of phloroglucinol or barbituric acid, for the determination of 

 pentoses and pentosans. 



Methods in soil analysis, F. E. Bear and R. M. Salter (West Virginia Sta. 

 Bui. 159 (1916), pp. 3-2Jf, figs. 2). — This bulletin outlines in detail methods for 

 complete soil analysis which have been found reliable by their successful use 

 in several hundred analyses of various types of West AMrginia soils. 



The estimation of thiosulphate sulphur in lime-sulphur solutions by iodin 

 titration, P, L. Blumenthal and S. D. Averitt (Jour. Amer. Chem. Soc, 38 

 (1916), No. 9, pp. 1701-170>4). — From a study carried on at the Kentucky Ex- 

 periment Station, the authors conclude that " an excess of iodin does react 

 with tetrathionate in neutral or faintly acid solutions upon standing. In every 

 iodin titration on a lime-sulphur solution a small quantity of sulphate is 

 formed ; in some lime-sulphur solutions this is the only sulphate found. 



*' The quantity of iodin used to form sulphate in an ordinary titration does 

 not cause an appreciable error in the determination of thiosulphate. The iodin 

 value obtained after decomposing polysulphids by HOI titration actually rep- 

 resents thiosulphate, since the barium sulphate obtained irom such solutions 



