132 BELL SYSTEM TECHNICAL JOURNAL 



Determination of Small Amounts of Arsenic, Antimony, and Tin in Lead 

 and Lead Alloys.^ C. L. Luke. A new method for the determination of 

 small amounts of arsenic, antimony, and tin in lead and lead alloys consists 

 of separation of the three metals from the lead by a double co-precipitation 

 with manganese dioxide, reduction of arsenic and antimom^ to the trivalent 

 state, separation of the arsenic by distillation as chloride, titration of the 

 arsenic and antimony separately by the method of Gyory, and reduction 

 of tin with lead and titration with standard iodine solution. 



Determination of Total Sulfur in Rubber} C. L. Luke. A new volumetric 

 method has been developed for the determination of sulfate sulfur. The 

 sulfate is reduced to sulfide by treatment with hydriodic acid and the h}-dro- 

 gen sulfide is distilled oflf and titrated iodometrically. The new method has 

 been applied to the determination of total sulfur in natural and synthetic 

 rubber. 



Machine Screws. Fastening Strengths in Various Materials.^ A. C. 

 Millard. Although standard machine screws in the numbered sizes have 

 been widely used as fastenings for many years, very little has been published 

 concerning their strength of fastening in various metals and non-metals. 

 Numerous articles have appeared regardmg the strength of bolts and ma- 

 chine screws for j in. and larger sizes, but very little, if any, published in- 

 formation is available on the strength of machine-screw fastenings in the 

 numbered sizes. 



The need for machine-screw fastening-strength information has increased 

 recently due to the use of more compact designs and the shortage of mate- 

 rials. The use of substitute materials has accentuated the lack of machine- 

 fastening-strength information in making fastenings in such materials, as 

 well as in the more commonly used materials. Frequently, it is desirable 

 to know the load-carr>ang capacity of screw fastenings of various diameters, 

 as well as the length of thread engagement in the weaker materials needed 

 to develop either the full strength of the screw, or the strength of fastening 

 required of the assembly. The purpose of this paper is to make available 

 to designers the results of fastening-strength tests of machine-screw fasten- 

 ings in a number of materials, which were carried out by the author at the 

 Bell Telephone Laboratories, Inc. The work is by no means complete but 

 is hoped that the data offered will prove to be of some use in its present form. 



^ Indus. & Engg. Chemistry, October 1943. 

 ^ Indus. & Engg. Chemistry, September 1943. 

 « Mech. Engg. October 1943. 



