174 The Philippine Journal of Science i9i6 



is required for the actual operations. I have never had much 

 success in determining lead as chloride according to Walker and 

 Whitman's method, or in determining it directly as sulphate as 

 suggested by Demorest.^ 



COPPER 



In many babbitts the copper content is less than 0.5 per cent. 

 In this case a colorimetric method has been found to be suffi- 

 ciently accurate. It is best to use as a standard a babbitt of 

 known copper content. Weigh equal portions of the standard 

 and sample and dissolve in a small quantity of nitric acid of 

 1.20 specific gravity. After diluting with about 10 cubic centi- 

 meters of water, neutralize with ammonia and add about 5 

 cubic centimeters in excess. After cooling, dilute the solutions 

 to definite volume, 25 or 50 cubic centimeters, and filter into 

 color carbon tubes having large diameters. By diluting as in 

 the method of reading color carbons, the percentage of copper 

 may be estimated. If a precipitate forms on diluting a solu- 

 tion of the sample or standard, it should be filtered out, using 

 a dry filter, before making a final reading. If the copper ex- 

 ceeds 0.5 per cent, it may be determined by some modification 

 of the cyanide method or the iodide method of Low.* The former 

 is more satisfactory if the percentage of copper is low, while 

 the latter is better for a higher percentage. 



IRON AND ZINC 



Iron is present in practically all babbitts, although usually 

 the percentage is less than 0.1. To determine the iron, the 

 filtrate from the lead sulphate may be utilized. Dilute this 

 filtrate to about 300 cubic centimeters, heat to boiling, and 

 saturate with hydrogen sulphide. If any precipitate is formed, 

 filter and wash with hot hydrogen sulphide water. Partly 

 evaporate the filtrate to expel the gas and boil with the addition 

 of a few drops of nitric acid. Precipitate the iron by neutraliz- 

 ing with ammonia and determine as ferric oxide. 



As a rule zinc is present in only small amounts — usually less 

 than 0.1 per cent. It may be determined in the filtrate from 

 the iron. 



PREPARATION OF A STANDARD BABBITT METAL 



The standardization of the various volumetric solutions men- 

 tioned above may be advantageously effected by the use of stand- 



'Joum. Ind. & Eng. Chem. (1913), 5, 842. 

 * Journ. Am. Chem. Soc. (1896), 18, 458. 



