PHENYLARSONIC ACID AS A QUALITATIVE TEST FOR TIN R. H. BULLARD Hobart College, Geneva, New York
IN THE separation and qualitative detection of tin, tional qualitative procedure the following method is one of the commonly employed methods is to sepa- used. rate it as Group IIB along with arsenic, mercury, and The Group IIB sulfides are heated with 12 N hydroantimony by use of sodium or ammonium sulfide'rea- chloric acid as usual. The antimony and tin sulfides gent. These metal sulfides are then reprecipitated with dissolve and the filtrate containing these metals is dlacid, filtered, and partially dried. The antimony and luted with water according to the customary procedure. tin sulfides are dissolved out with 12 N hydrochloric Five cubic centimeters of this solution are taken and acid. The antimony is separated and the tin tested for heated to boiling. To this hot solution are added ten in the remaining solution. cubic centimeters of a solution of phenylarsonic acid,' We have noticed that students experience difficulty containing forty grams of phenylarsonic acid per liter in detecting tin by this procedure. As a matter of fact, of water, which has also been heated to boiling. A more errors are made a t this point than at any other cloudy white precipitate of metastannic acid appearing place in the entire analysis. A more certain test for tin almost at once is the test for tin. If the solutions are cold, seemed desirable, especially if it could be adapted to antimony oxychloride will of course precipitate, but in the conventional scheme of analysis. hot acid the antimony remains in solution. Knapper, Craig, and Chandlee' state that tin is preWe have used this test in our classes for the last two cipitated quantitatively by adding to a hot acid solution years and, as a result, the errors in reporting tin have of the metal a saturated solution of phenylarsonic acid. almost entirely disappeared. To apply this quantitative precipitation to the conven-
-
' KNAPPER,CRAIG.AND
3945 (19331,
CHANDLEE, I. Am. Chem. Soc., 5 5 ,
Phenylarsonic acid may be obtained from the Eastman Kodak Company or it may be prepared according to directions in "Organic Syntheses," Vol. 15, p. 59.
