610 EXPERIMENT STATION RECORD. 



Strongly calcareous soils on the composition of the ash of 7 samples of cassava 

 roots and stems, a comparison was made of the acetate method for estimating 

 calcium and the official method. The former method consists of precipitating the 

 iron and aluminum present as phosphates with ammonium acetate in a slightly 

 acid solution and then precipitating the calcium as oxalate, thereby avoiding 

 the reprecipltation of a bulky precipitate of ferric phosphate. In the acetate 

 method the ferric phosphate precipitate is small, is easily handled, and does 

 not have to be reprecipitated. 



It was found " that the acetate method is fully as accurate as the official 

 method for the determination of lime and magnesia in plant ashes. Since these 

 samples contained from 15 to 18 per cent of P2OS and only 0.63 to 1.72 per cent 

 of Fe203, it is evident that only a small portion of the phosphoric acid was 

 removed before the precipitation of lime in the acetate method, and that the 

 further addition of ferric chlorid, with its attendant difficulties, as prescribed 

 by the official method, is unnecessary." 



Apparatus for the detection of carbon monoxid, M. A. Guasco (Compt. 

 Rend. Acad. 8ci. [Pans], 155 (1912), No. i, pp. 282-28^^; abs. in Analyst, 57 

 {1012), No. 43s, p. 426). — With the apparatus described as little as 1 part 

 carbon monoxid in 10,000 may be detected. 



" Two bulbs, one of which is platinized, are carried at the extremities of a 

 vertical U-tube, and are inclosed in a gas-tight envelope, to which the gas to 

 be examined is admitted through a porous septum. The portion of the U-tube 

 outside the envelope contains a colored liquid, and is so arranged that very 

 small differences of level, produced by differences in temperature of the bulbs 

 due to occlusion of inflammable gases by the platinum, are readily observed. 

 With the apparatus used, the difference in the levels in the two limbs produced 

 by 1 volume of carbon monoxid per 1,000 was 13 mm., and by 2 in 1,000, 26 

 mm. ... If mei-cury is substituted for the colored liquid, the apparatus can 

 readily be arranged to close a circuit and thus release an alarm signal." 



The determination of nitrates in soils and soil estracts, H. H. Hnx (Vir- 

 ginia Sta. Rpts. 1911-12. pp. 133-lU).— The zinc-iron reduction method, the 

 Tiemann-Schulze method, and the colorimetric method were compared. 



The results show that " in pure solutions of potassium nitrate each one of 

 the 3 methods tried gave excellent results through 9 mg. of nitrate nitrogen 

 calculated as N; but beginning at 10 mg. and continuing through 40 mg., only 

 2 — the reduction and Tiemann-Schulze methods — gave satisfactory results. The 

 results obtained in using pure nitrate solutions were found to be true when 

 soils to which nitrates had been added were examined. It is probably better to 

 use the colorimeter method for all quantities of nitrate nitrogen not over 9 mg.. 

 this method being very rapid, and also making very expensive reagents and 

 apparatus unnecessary. From 10 mg. of nitrogen to 40, the reduction and 

 Tiemann-Schulze methods are the most accurate. 



" Organic matter has a marked effect upon the Tiemann-Schulze method. 

 This is especially true of the carbohydrates. When soils contain amounts 

 larger than those usually found in our eastern soils, especially those of Vir- 

 ginia, or soils which have received a green manure, it is best to use a modifica- 

 tion of this method to correct the error due to the presence of organic bodies. 

 Virginia soils are very deficient in nitrates, the average amount in every 100 

 gm. of dry soil being about 1 mg. The colorimetric method gave excellent 

 results on these soils, and it is thought expedient to use this method whenever 

 possible. There is very little variation in the reading of the colorimeter by 

 different observers when freshly prepared standards and a reliable colorimeter 

 are used." 



A bibliography is appended. 



