BULLETIN OF THE 



ii 



No. 163 



Contribution from the Bureau of Animal Industry, A. D. Melvin, Chief. 

 January 12, 1915. 



A FIELD TEST FOR LIME-SULPHUR DIPPING BATHS. 



By Robert M. Chapin, 

 Senior Biochemist, Biochemic Division. 



INTRODUCTORY. 



The purpose of this paper is to describe a portable testing outfit 

 devised by the writer and employed by the Bureau of Animal Industry 

 for estimating the strength of lime-sulphur dipping baths used in 

 official dipping under regulations now in force. 1 A description of 

 the outfit will be of interest to Federal and State officials concerned 

 with the supervision of dipping, to private parties who wish to control 

 the composition of their dipping baths, and to manufacturers whose 

 dips are subjected to test. This method, however, is intended only 

 for field use ; it can not replace in the laboratory the more accurate 

 methods of analysis approved by the Association of Official Agricul- 

 tural Chemists. 



Lime-sulphur dipping baths, whether homemade or proprietary, 

 are essentially composed of two substances in solution, both of 

 which contain sulphur, namely, calcium polysulphid and calcium 

 thiosulphate. The Bureau of Animal Industry has no present proof 

 that calcium thiosulphate is of any value for the treatment of scabies 

 in either cattle or sheep, and pending further investigation, accord- 

 ingly, must attribute the efficiency of dipping baths solely to the 

 sulphur present in the form of calcium polysulphid. 



Many factors may influence the strength of lime-sulphur dipping 

 baths. In the first place, one of the raw materials, lime, is a sub- 

 stance of notoriously uncertain composition as commercially obtain- 

 able, and, further, it deteriorates on storage, so that a homemade 

 concentrated dip may turn out much weaker than its maker has 

 cause to suppose. In the second place, solutions of calcium poly- 

 sulphid are decomposed by contact with air, so that a bath may 

 notably deteriorate even during a single day's dipping. In the 



1 Bureau of Animal Industry Order 210, issued June 18, 1914; reg. 3, sec. 9, p. 19, and reg. 4, sec. S, p. 23. 



Note. — This bulletin describes a portable testing outfit for estimating the strength of lime-sulphur 

 dipping baths; it is of interest to makers and users of such baths, as well as to officials charged with the 

 enforcement of dipping regulations. 

 66920"— 15 



