806 EXPERIMENT STATION RECORD. [Vol.40 



The author considers the method of Barnett and Chapman, previously noted 

 (E. S R., 39, p. 9), satisfactory for the determination of the hydrogen-ion 

 concentration of media in routine laboratory work, but suggests slight modifica- 

 tions, including the use of a 0.04 per cent solution of brom thymol blue as an 

 indicator. 



A mechanical pipette for easy measurement of small volumes, H. C Bazett 

 {Jour. Physiol, 52 (1919), No. 5, pp. LXI, LXJI, figs. 2).— A pipette devised for 

 the rapid and accurate measurement of amounts of fluid as small as 0.0ft cc- 

 is described and illustrated. 



The pipette is made by heating a fine bore, thick-walled glass tube to form 

 two constrictions of capillary bore. One of these constrictions is plugged with 

 a small wad of cotton wool, and mercury is drawn up to fill the space between 

 the constrictions. The mercury is discharged into a watch glass. 0.05 cc. (or 

 the volume to which the tube is to be adapted) is deducted, ami 1 1 i ♦ • remainder 

 is again drawn up into the tube. The other capillary end is then plugged with 

 cotton, the mercury forming a valve which prevents the entrance into the tube 

 of a larger volume of liquid than that of the mercury discarded. 



It is necessary in actual practice to standardize each pipette. With proper 

 precautions the errors are said to be less than -f 0.2". per cent. 



Protection against drip water in an extraction apparatus, F. Liehkrt (Chi m. 

 Weekbk, 16 (1919), No. 3, p. 7.J).— To prevent water that collects on the outside 

 of the condenser from dripping on the extraction flask, it is recommended that 

 the lower part of the condenser be covered with a paste made from shredded 

 filter paper, powdered calcium carbonate, ami a solution of calcium hydroxid. 

 After hardening, this paste will absorb the water that tends to collect on the 

 surface. 



Picramic acid as a standard in colorimetric determination of nitrogen by 

 Nessler's method. G. Egerkb and F. Ford (Jour. Lab. and Clin. Mel.. 4 (1919), 

 No. 7, pp. 439-4 /-). — The disadvantages of Nessler's reagenJ aa a standard in 

 the colorimetric determination of nitrogen by Nessler's method are pointed out, 

 and the sussestion is made that for clinical work the blood sugar standard, 

 picramic acid, be used in place of Nessler's reagent It is said that nil color 

 comparisons in which Nessler's test can be used can be made as readily by pic- 

 ramic acid, the color of which is practically permanent. 



A process of purifying picric acid is described, and attention is called to the 

 modified method for the preparation of picramic acid previously noted (E. S. 

 R., 40, p. 203). 



A scrubber for ammonia distillations. B. S. IUvisson (Jour. Indus, and 

 Engin. Chem., 11 (1919), No. 5, pp. 465, 1,66, figs. 2).— This contribution from the 

 Ohio Experiment Station describes in detail the scrubber which is one of the 

 features of the all-glass nitrogen apparatus described by Allen and Davisson 

 (E. S. R., 40, p. 809). 



The device consists of a 200 cc. bulb of I'yrex glass, the inlet rube of which 

 Is provided with a small bulb bavins three openings in the same horizontal 

 plane. The first steam which passes into the scrubber condenses on the surface 

 of the large bulb and flows down about the small bulb, actios there as a scrub- 

 bing solution for the remaining vapors. Diagrams are given of the device and 

 of a special adapter provided with a small perforated bulb, which is said to 

 Insure better scrubbing of the steam than is accomplished with a straight tube. 



Kecovery of platinum and alcohol from the potash determination, A. F. 

 Smotx (Jour. Indus, and Engin. Chem., 11 (19t:l), No. 5, pp. 466. 467). — The 

 method involves first a distillation of the alcoholic washings, with resulting re- 



