NOTES i l N D CORRESPONDENCE. was determined as sulphate and, for comparison, as pyrophosphate by the method given by iyaring.' I n these determinations the solution for analysis was measured out by one of the writers and the determination made by the other, so t h a t the analyst had no knowledge of the result which he was expected to get. TABLEI. DETERMINATIOIS O F ZINC
AS SULPH.4TE
A N D PYROPHOSPHATE,
0.3043 g. zinc. 0.1541 0.0909 0.2428 As pyrophosphate. 0.2861 g. zinc. 0.1656 0.2224
furnishes increased surface for filtering but also allows the denser part of the precipitate to settle in a ring a t the bottom of the crucible, leaving the asbestos on the apex of the filter in such a condition that the filtrate and washing liquids can be quickly and completely removed. B. hfE.4RS. UNIVERSITYO F ILLINOIS, b f A Y 31, 1909
WITH
CALCULATEDRESULTS. Found. -4s sulphate.
477
Calculated. 0.3035 g. zinc. 0.1533 0.0909 0.2425
THE DETERMINATION OF OXIDES OF IRON AND ALUMINA IN FLORIDA PHOSPHATES.
The method as given below is a modification of the old Glaser method, and can be depended upon to give excellent results in all except the few instances in which manganese occurs in any appreciable quantity. It must also be noted 0.2854 g. zinc. that this method does not include any iron or alumina present 0.1656 in the shape of pyrite, or as a silicate insoluble in acid. 0.2223 TVith reasonable care in the various operations, the results T o determine whether or not the presence of small quan- on the identical pulverized sample should not differ more tities of ammonium chloride affects the result, either by than 0.05 per cent. and are generally well within this limit. remaining unvolatilized a s sulphate or by causing volatiliza- The most important points appear to be the proper elimination of zinc chloride, zinc chloride solutions were evaporated tion of fluorine, and the use of vel.? hot water in washing the with sulphuric acid and a few milligrams of ammonium chloprecipitate. As carried out in this laboratory, the operations ride. The outcome of these experiments (Table 11) makes are as follows: i t clear that for this determination it is not necessary to One gram of the powdered sample is carefully weighed wash precipitated zinc sulphide perfectly free from ammonium out and placed in a tall beaker of about 300 cc. capacity chloride which may contaminate it. It should be added, Ten cc. of strong muriatic acid are added, and after covering however, t h a t larger quantities of ammonium chloride ( IOO with a watch glass, the beaker is placed on a gauze and quickly nig. and over) cause low results. brought to a boil. Leave on the gauze for ten minutes, TABLE11. regulating the flame so that it does not go dry, and the bulk INFLUENCE O F AJ.IMONIUM C H W R I D E O N DETER~IINATION O F Z I N C AS of the solution a t the end of the ten minutes is about 5-7 cc. SULPHATE. Let cool, and carefully decant as completely as possible into Found. Calculated. a Jena glass volumetric flask of IOO cc. capacity. Try to 0.1803 g. zinc. 0.1803 g. zinc. get all the solution to run into the flask, excepting the last 0.1804 0.1804 EUGENEC. SULLIVAN, drop or so. Rinse this last drop into the flask with the least possible amount of water. It is possible to do this with a 1%'. C. TAYLOR. little practice, without disturbing the bulk of the sand, CORNINGGLASSWORKS, CORNING,X. Y . which remains (most of it) in the original beaker. You now have about IO-IZ cc. solution in the little volumetric flask. To this solution in the flask you add 10cc. of dilute sulphuric THE PREPARATION OF GOOCH CRUCIBLES FOR acid (one-half acid of 1.84sp. gr., and half water). ASPHALT ANALYSIS. The addition of this acid will form a curdy, bulky precipiThe filtration of tarry or asphaltic precipitates suspended tate of impure sulphate of lime. Shake up the flask to mix in organic solvents on porcelain Gooch crucibles is a tedious this precipitate, and then place the flask on a gauze over and unsatisfactory process at best. The following simple Bunsen in the hood, and boil for a t least ten minutes. deviation from the ordinary method of preparing such I t may require a little practice to get the flame just right, crucibles has proven itself of value in several hundred deterto get the flask and contents t o boil hard vithout bumping minations carried out in this laboratory. off the stand-but i t is most important that the contents should boil, This boiling gets rid of nearly all the fluorine, CRUCIBLE and changes the bulky precipitate of calcium sulphate into ASBESTOS a dense, crystalline compound, which filters and washes easily. My experience has been t h a t a gauze and Bunsen pf. COWP are better than hot plate or sand bath for this particular operation, a s a quick heat gets the solution to a temperature TARRY where the violent pumping (caused by the occasional liberation of a large bubble of vapor) is avoided by causing the evolution of steam, etc., to be so rapid as to form a more A thimble-shaped cone of platinum gauze is placed in the continuous stream. bottom of a Gooch crucible and the asbestos sucked dry over After ten minutes' boiling, take the flask off the fire and i t as shown in the accompanying cut. In cases where i t is let cool to room temperature. not necessary to ignite the precipitate, fine copper gauze To go back to the beaker in which the original solution has proven itself satisfactory. I n use, the cone not only was made, it is possible t h a t the grains of sand and insoluble 1 Jour. of the Amer. C h m . S o c . , 26. 28 (1904). matter might not have been rinsed quite clean in transferring to
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