204 EXPERIMENT STATION RECORD. [Vol. 38 



nock of the flask, and although it became hard during tlie distillation could be 

 removed without difficulty. By moistening again it could be used for a second 

 distillation. 



An accurate method for taking aliquots of a standard in standardizing 

 solutions, C. F. Miller {Jour. Amer. Chetn. Soc, 39 (1917), No. 11, p. 2388).— 

 The following method is proposed: 



About five times as much of the standard as is desired for the titration is 

 carefully weighed and dissolved in a quantity of water slightly exceeding five 

 times the capacity of the pipette to be used in taking the aliquots. Five por- 

 tions of the solution are then carefully drawn in an identical manner, and the 

 remainder, together with the rinsings from the pipette, is transferred to a 

 tared platinum dish, evaporated, dried, and weighed. The pipette need not be 

 standardized nor Its exact capacity known. A simple calculation gives the 

 amount of material in each aliquot. 



The method can be used only for such substances as sodium carbonate, 

 sodium oxalate, etc., which are soluble and separate from the solution again 

 in a weighable form upon evaporation. 



The nomon — a calculating device for chemists, H. G. Deming (Jour. Amer. 

 Chctn. Soc, 89 (1917), No. 10, pp. 2137-21^, figs. 2).— The author describes the 

 use of a calculating chart which he has devised and which has a degree of pre- 

 cision about five or ten times that of an ordinary 10-in. slide rule. Special 

 scales can be easily constructed to adapt the chart for varied calculations. 



Observations on the McLean- Van Slyke iodometric method for the titra- 

 tion of small amounts of halids, in its application to chlorids, R. F. Mc- 

 Cracken and Mary D. Walsh (Jour. Amer. Chem. Soc, 39 (1917), No. 11, pp. 

 2501-2506). — Tlie authors have found that when a titration is made very slowly 

 in the McLean-Van Slyke method ^ a starch-iodid color that might be mistaken 

 for the end point sometimes develops before the titration is complete. This 

 color gradually disappears as the end point is approached, even when several 

 times as intense as the end point color. By supplementing the starch present 

 in the titration with 10 cc. of a 1 per cent soluble starch solution just before 

 titration, the end point is obtained in a clear solution instead of an opalescent 

 solution. 



Both the original method and the method with the use of additional starch, 

 as noted above, are indicated as giving satisfactory results. 



Determination of chlorin in hlood serum and albuminous body fluids, 

 M. Laudat (Jour, rharm. ct Chim., 7. scr., 16 (1917), No. 6. pp. 168-171).— In 

 the titration of chlorin after oxidation with nitric acid the development of the 

 yellow color during the action of the nitric acid on the protein was found to 

 interfere with obtaining a sharp end point and consequently caused slightly low 

 results. The use of potassium permanganate was found to eliminate this 

 source of error and the following procedure was developed : 



To 5 cc. of the serum or other sample 10 cc. of tenth-normal silver nitrate, 

 6 cc. of a saturated solution of potassium permanganate, and 10 cc. nitric acid 

 (specific gravity 1.38) are added and the mixture carefully heated for several 

 minutes. After cooling, the liquid is made up to 100 cc. volume and the excess 

 .■silver nitrate titrated with tenth-normal potassium sulphocyanate, using ferric 

 alum as indicator. It is noted that the procedure requires but five or six min- 

 utes for completion, and yields accurate results as shown by comparative data. 



The colorimetric determination of manganese by oxidation with periodate, 

 H. 11. WiLLARD and L. H. Greathouse (Jour. Amer. Chem. Soc, 39 (1917), No. 

 11, pp. 2366-2377). — A method based on the equation 



2Mn(N03)=+5KI04+3H20=2HMn04+5KIOs+4HN03 



iJour. Amer. Chem. Soc., 37 (1915), No. 5, pp. 1128-1134. 



