62 TESTING MISCELLANEOUS SUPPLIES. 



The character of the record is given a maximum rating of 20 ; life or durability 

 of the ribbon, 10; resistance to reagents, 20; and resistance to sunlight, 45. 

 Ribbons rated below 5 on typefilling or below 18 on character of record are 

 rejected without further test. 



CARBON PAPERS. 



The practical testing of carbon papers consists in making a carbon copy on 

 the special machine used for testing the life of ribbons, using a good quality of 

 medium weight writing paper, such as is used in testing typewriter ribbons. The 

 record is examined in the same manner as the ribbon record and is rated as 

 follows : 



Character of record 35 



Resistance to reagents 20 



Resistance to sunlight 45 



Total maximum 100 



No test need generally be made of the life of a carbon paper, since when 

 struck in the same place all papers are very soon exhausted, no practical dif- 

 ference in this respect having been observed. Of course in actual use a number 

 of impressions can be made, since the type seldom strikes in the same place. 



MISCELLANEOUS. 



BABBITT METAL (RAPID ANALYSIS)." 

 1. Copper. 



Weigh 1 gram of the alloy into a 250 cc beaker, add 20 cc of hydrochloric acid 

 and 5 cc of water, heat, and complete the solution by adding nitric acid in small 

 amounts; with most alloys solution can be effected in a very few minutes and 

 without adding more than 1 or 2 cc of nitric acid. Evaporate off the acid on a 

 st. ;! in bath. It is not necessary to carry to complete dryness, but practically 

 all the acid should be driven off and the residue should be pasty. Add 25 cc of 

 a solution made of 200 grams of tartaric acid and 260 grams of potassium 

 hydroxid, the whole being made up to 500 cc with water. Heat on the steam 

 bath until solution is completed, add 25 cc of water, boil, add 25 cc of a 0.2 per 

 cent Invert sugar solution, boil for two minutes, filter through asbestos, wash 

 the precipitate of cuprous ox id with water, dissolve in nitric acid, catching the 

 copper solution in a 200 cc flask, and determine copper by any good volumetric 

 method. Equally good results can be obtained by following Low's iodid method,* 

 or Jamieson, Levy, and Wells's thiocyanate and iodate method. The results 

 nre uniformly a little low. This error is not due to the volumetric methods 

 employed, both of which give exceedingly accurate results, but to the fact that 



y ; i>er cent of the copper present is not precipitated as cuprous oxid. 

 This loss is uniform, for if we add 6 per cent of the copper determined, the 

 result will be the per cent of copper in the alloy. 



Tin- statement is frequently made that if a babbitt metal is decomposed by 

 nitric acid, evaporated to dryness, taken up with nitric acid and filtered, copper 



1 determined in the filtrate with an error of not more than one or two 

 tenths of 1 p<-r cent. This is not the case, ns the error with an alloy containing 



r cent of cop^r will frequently he from o.r, to 0.7 per cent, while by th 



<MV:ilker ;md Whitman. J. Ind. Kiip. Chem., 1909, 1:519. 

 6 J. Amer. Chem. Soc., 1902, 24: 1082. 

 c lbid., 1908, 30:760. 



