A S A L Y T I C AL E D I T I O S
1%
Vol. 2 ,
so.2
test drop of this solution add a kernel of potassium nitrite. Black cubes show the presence of lead (Figure 7 ) . 2-Add a drop of nitric acid to the second portion, warm, and add a kernel of silver nitrate. Prismatic crystals of varying shades of red indicate the presence of chromium. (Figure 8)
thiocyanate. Blue clustered needles show presence of cobalt. (Figure 6) To another test drop of the ammoniacal solution, add a kernel of dimethyl glyoxime. Red or pink needles show the presence of nickel. (See note 4 under Separation.) GROUPIV-Acidify the solution with hydrochloric acid and add sodium sulfite and boil. Add ammonium thiocyanate solution, cool, and filter. Residue: Copper thiocyanate. Dissolve in ammonia and add mercuric chloride. Green clusters of radiating needlrs shorn the presence of copper. (Figure 10) Filtmte: Chlorides of zinc, cadiiiium, nickel, and magnesium. Make solutioii a 1k a li ne w i t h ammonium liyclrosidc. Divide into three parte: 1-To the first part acid ainiiioiiiuiii niercuri-t,hiocyanate. Feathered m i s s e s indicate zinc; colorless prisms ~ I ~ C the JW p r e s e n c e of c a d m i u m ; triangular or arrowhead-shaped crystals slion prwencc of both zinc and cadmium. (Figures F i g u r e 13-Mercuri-thiocyanates Figure 14-Ammonium Magnesium of Zn a n d Cd ( 1 : l ) 11, 12, and 13) PhosDhate i-To the second portion add kernel (Jf 3-Add a few drops of concentrated hydrocliloric acid and dimethyl glyoxime. Pink or red needles show the presence to a test drop add a very small amount of concentrated cae- of nickel. 3-Add kernel of ammonium phosphate to the third part. sium bisulfate solution. The colorless alum crystals indicate the presence of aluminum. (Figure 9) Characteristic four-armed feathery crystals of ainnioniurn magNote-(l) If lead and chromium are both present, lead nesium phosphate shorn presence of magnesium. (Figure 14) chromate will be precipitated upon acidifying the solution and Literature Cited no further tests for these two metals are necessary. (1) Behrens and Klep, "biikrochemische Analyse," 1'01. I. GROUP111-Fuse part of the precipitate with sodium car- (2) Chamot, "Elementary Chemical hlicroscopy," 2nd ed., p . 414. bonate and sodium nitrate o n a platinum spoon. A green (3) Emich, "Lchrbuch der SIikrochernie," 2nd e d . , p , 8. 173 (4) Longinescu and Chaborski, Bd1. ciiim. pure a p p l . , 26, 3 (1023; ; Client. color shows the presence of manganese. Z e n f v . , 95, 944 (1924). Dissolve the remainder of the precipitate in hydrochloric ( 5 ) Martini and Shamis, "Trabajos al seEundo congreso de guimica l3ueno3 acid and neutralize with ammonium hydroxide; filter if Aires," 1924. necessary. To a test drop add a drop of ammonium mercuri- (6) Zepf, J2eta1lbOrse. 13, 65% (1923).
Substitute for Amalgamation in Testing Bituminous Materials for Melting Point, Ductility, and Float Test' Hans Eisner IllPERIAL
OIL REFISERIES, LTD.,S A R S I A , OST.
HE melting point (S), ductility (1, S), and float ( A ) tests for bituminous materials are performed in most laboratories by indii7iduals without chemical training. and large quantities of mercury are often left on the plate after amalgamation. Stock ( 2 ) has shonn that 1 cubic meter of air containing 0.001 mg. of mercurial vapor is injurious to health and chronic poisoning will result n-ith prolonged contact. The layer of mercury on the plate mhen coming in contact with the hot bituminous material gives off poisonous mercurial vapors and, as a result, not only the man who is working with it, but also other people, are affected. I n the writer's laboratory an attempt was made to replace this amalgamated plate. The first experiments were with highly polished plates, in the hope that the sample could be easily removed. These attempts failed, as the asphalt stuck tenaciously to the plate, showing that the mercury forms an isolating film between the asphalt and the plate. The next experiment was to cover the plate with a material which must form a thin layer soluble in water-e. g., glycerol. This gave better results. It was observed, however, that the glycerol would not retain a continuous film if the plate 1
Received January 11, 1930.
wa3 polished. The application of glyccrol to a rough, unpolished plate gave better results. Should the surface of the brass plates be too smooth, the surface should be first cleaned and then etched with acid. On applying the glycerol to the surface prepared in this manner, it was found that the film remained unbroken; in fact, a great improvement over a rough, untreated surface was noted. The molds and rings could be taken off the plate with greater ease than when mercury solution had been applied for amalgamating. I n this laboratory etched plates of brass and staiiilesa steel give perfect satisfaction. All impurities are removed from the surface with solvent naphtha, carbon bisulfide, or carbon tetrachloride before applying the glycerol, one drop of xhich is quite sufficient to coi-er one square inch of surface. The quantit,yof glycerol is small and the worker is, a t all times, free from danger of acid burns or mercury poisoning. I n this laboratory the amalgamation of plates and molds has been replaced entirely by the use of glycerol. (1) Am. SOC. Testing Materials, Tentative Method D113-26T (1828). (2) Stock, Z. a n g e v . Chem., 41, 663 (1928). (3) U. S. Dept. Agr., Bull. 1216, Method 53, p. 81. (4) Ibid., Method 50, p. 79.
