BABBITT METAL (RAPID ANALYSIS). 53 



method just described without correction tin- error will be less than 0.3 per cent, 

 and by applying the correction this error is removed entirely. 



2. Lead. 



Dissolve 0.5 to 1 gram of alloy in a 250 cc beaker as in the determination 

 of copper; when solution is complete evaporate to dryness on the steam bath, 

 add 5 cc of strong hydrochloric acid (with as much as 10 per cent of anti- 

 mony use 10 cc of hydrochloric acid), warm for a few minutes, remove from 

 steam table, add, with stirring, 150 cc of 95 per cent alcohol, let stand at room 

 temperature for two hours, filter on a Gooch crucible, and wash with 95 per 

 cent alcohol, using about 100 cc. Suck as dry as possible, dry crucible in an 

 air bath (one hour at 105 C. is sufficient, though the lead chlorid can be 

 heated at 150 with perfect safety). Weigh as lead chlorid, add 0.0085 gram 

 to the weight of the precipitate, and multiply by 0.74473; the product gives 

 the weight of lead. 



3. Antimony. 



Antimony is determined by W. H. Low's method slightly modified as fol- 

 lows: To 1 gram of alloy in a 450 cc Erlenmeyer flask add 10 to 15 cc of 

 strong sulphuric acid, and heat on a hot plate until the alloy is thoroughly 

 decomposed. This is generally accomplished in about thirty minutes from the 

 time fumes of sulphur trioxid begin to be given off. Cool, add 200 cc of water 

 and 20 cc of strong hydrochloric acid, boil to make sure that all sulphur dioxid 

 is driven off, cool and titrate rapidly with potassium permanganate which 

 has been standardized against metallic antimony. The true end-point is found 

 when a pink color shows after agitating the liquid, though this pink will very 

 soon disappear. The only change made in the Low method of procedure is 

 to add somewhat less hydrochloric acid. The results are sufficiently accurate 

 for commercial purposes, but the tendency is to get results 0.3 to 0.4 per cent 

 high. 



4. Tin. 



Tin is also worked by W. H. Low's method, except that it seems to be more 

 satisfactory to use a separate portion of the alloy and reduce with steel 

 turnings instead of with metallic antimony. Treat from 0.2 to 1 gram of alloy 

 (do not use an amount of alloy containing more than 0.2 gram of tin) in a 

 450 cc Erlenrueyer flask with 10 to 15 cc of strong sulphuric acid, heat on the 

 hot plate until the alloy is thoroughly decomposed, cool, add 200 cc of water, 

 30 cc of strong hydrochloric acid, and about 1 gram of steel turnings, heat, 

 and when reduction appears complete, but before the last particles of steel 

 have dissolved, place a two-hole rubber stopper in the neck of the Erlenmeyer 

 flask one hole of the stopper should carry a tube reaching below the surface 

 of the liquid, the other hole should carry the short arm of a bent tube, the 

 long arm of which reaches nearly to the bottom of a 100 cc Erlenmeyer flask 

 containing a solution of sodium bicarbonate. This small erlenmeyer is 

 held on the bent tube by a cork which has a notch cut in it to act as a vent. 

 Through the tube reaching below the surface of the liquid in the large erlen- 

 meyer pass a current of carbon dioxid, heat to boiling until all steel is dis- 

 solved, continue passing carbon dioxid, and cool as quickly as possible; loosen 

 the stopper but let the current of carbon dioxid continue ; add cautiously some 

 starch solution and titrate with tenth-normal iodin. It is necessary to abso- 

 lutely exclude air and to standardize the iodin solution with pure tin. 



J. Amer. Chem. Soc., 1907, 29 : GG. 



