834 EXPERIMENT STATION RECORD. 



ness, and heat 2 liours in the water oven. Add 5 cc. nitricarid and jji-occed as above. 

 Readings =P205. In this case siHca is not determined." « 



Varions precautions to be observed are noted and results of tests of the method are 

 reported which show that "there is a maximum error of ±2 scale divisions (each 

 scale division =1 cc. ) in the reading. When the soil solution is made by treating 1 

 part of i-'oil with 5 parts of water and 50 cc. are taken for the determination, the 

 crmr on the dry soil is ±2 parts per million cc. ; when 100 cc. are taken for the 

 determination, the error is ±1 part per million, so that the working errors may 

 only be neglected when at least 200 cc. of solution are taken for tlie determination." 



Determination of citric-soluble phosphoric acid in Thomas slag by the 

 molybdate method, 11. ^eujsauek { /(.schr. Aiujcir. Clicin., 15 ( lUO..'), Xo. 44, pp. 113.3- 

 1 L!.'>; (tli-s. in filial [/.^t, 'JS {190S), No. S'2S, p. 50). — The author recommends a molybdic 

 solution containing in 2 liters 150 gm. of ammonium molybdate and 1 liter of nitric 

 acid ( 1.2 sp. gr. ), since it is claimed that such a solution does not precipitate silicic 

 acid fniin the citric-acid solution of the slag. Moreover, the precipitation with this 

 ^olution is complete after 15 minutes' heating at 80° C. and 30 minutes' standing, 

 and the ]ircci]>itate is dense and easily waslied. 



Determination of phosphoric acid in Thomas slag-, (). Kellnek and (). 

 BoTTCiiEU [CJu'in. Ztij., 26 {1902), Xo. 97, p. 1151; abs. in Analyst, 2S {1903), Xo. 323, 

 p. 50). — If a precipitate which is not entirely soluble in hydrochloric acid is formed 

 by adding to the Wagner extract of the slag an ecpial volume of a reagent made by 

 dissolving 1,100 gm. of citric acid in water, adding 4,000 gm. of 24 per cent ammonia 

 and diluting to 10 liters, boiling for 1 minute, and allowing to stand 5 to 10 minutes, 

 the silica of the slag should be removed, before the phosphoric acid is precipitated 

 with magnesia mixture, by the Bottcher method (E. S. R., 0, p. 520). 



Chemical analysis of soils, R. Corr.\ui {Bol. Clilm. Farm., 41 {1!)02), pp. 410- 

 424, 675-G7S; <ihx. in Clicm. Ccnthl., 1002, II, Xo. 21, p. 1340). — This article discusses 

 methods of sampling and chemical and physical analysis. The calcium carbonate 

 content (.)f the soils is calculated from the loss of weight on treatment of the soil with 

 hydrochloric acid in a special apparatus which is described. Total phosphoric acid 

 is determined in nitric acid solution of the soil l)y multiplying the weight of ammo- 

 nium phosphomolybdate precipitate by 0.0355. In certain cases the phosphoric 

 acid, magnesia, potash, and soda combined with humus are determined. The direct 

 precipitation method of Corenwinder and Contamine is used for potash. 



A chemical method for determining the quality of limestones, A. M. Petek 

 {Jour. Amtr. Cheni. Soc, 25 {1903), Xo. 2, jyp. 143-150). — Proceeding on the theory 

 that the rapidity of disintegration of limestones depends upon the proportion of oxi- 

 dizable material — ferrous phosphate, organic matter, etc. — the author jiroposes to 

 measure the quality of limestones for building and road-making purposes by dissolv- 

 ing "the limestone in dihite sulphuric acid in the jjresence of a known amount of 

 potassium permanganate and determining how inncli permanganate has been reduced 

 during that process, after which the solution is to lie used for the determination of 

 phosphoric acid by a rapid volumetric method, and the insoluble residue for the 

 determination of the insoluble matter and clay." The details of the method are 

 explained, and the results of its use in the examination of a number of samples are 

 reported. "The conclusion would seem justified that the limestone which consumes 

 much more than 0.3 per cent of oxygen and at the same time contains as much 

 as 1 per cent of phosphoric acid, more especially if it contains also several per cent 

 of clay, will disintegrate i-apidly upon exposure to air and moisture and will be unde- 

 sirable for road l)uilding or other exposed construction." 



The determination of atmospheric carbon dioxid by the "Walker inethod, 

 A. G. Woodman {Jour. Amer. Chem. Soc, 25 {1903), No. 2, pp. 150-li;i, jlijx. 2). — 



""Or the organic matter maybe destroyed by treating with aqua regia in the 

 pre.'^ence of sutlicicnt base to prevent loss of phosphoric acid." 



