BYNE : THE CORROSION OF SHELLS IN CABINETS. 1 77 



V. — Prevention. 

 In the case of those shells which are badly affected, nothing can be 

 done, and their instant removal is absolutely essential, for if left they 

 only increase the mischief with those just beginning to shew signs of 

 corrosion. I recommend that they be soaked for twenty-four hours 

 n a solution of corrosive sublimate (i part in 1,000 water) and then 

 thoroughly dried. 



As an experiment all shells should be subjected to such a treat- 

 ment, in the hope that it may prove effectual. It is quite impossible 

 to say beforehand whether this will be an infallible remedy. Time 

 only can prove its efficacy. 



Summary. 

 1. — The corrosion is caused by the action of butyric acid upon 



the calcium carbonate of the shells. 

 2. — The butyric acid was derived originally from the decay of 



pieces of animal left in the shells. 

 3. — A subsidiary cause is the action of acetic acid, formed by the fer- 

 mentation of the gum, used in attaching the shells to the tablets. 

 4. — The white powdery substance upon the surface of the affected 

 shells consists of calcium butyrate, mixed in some cases with 

 a little calcium acetate. 

 5. — In all probability treatment with corrosive sublimate solution 

 (1 in 1,000) will prove an effectual remedy. 



Appendix. 

 The tests are numbered consecutively for convenient reference. 

 I. — The fine powdery substance was scraped off with a knife, care 

 being taken not to bring away any of the shell. 



1. — A small quantity was placed in a watch-glass, and a few drops 



of dilute hydrochloric acid added. No effervescence took 



place, thus shewing calcium carbonate to be absent. A most 



marked smell of vinegar was evolved, pointing to the presence 



of acetic acid. Probably some butyric acid was also present 



with it. 



2. — Another portion was heated strongly in a hard glass tube. 



Slight charring took place, owing to the presence of organic 



matter. An aromatic odour was given off, shewing presence 



of calcium salts of fatty acids (acetic and butyric). 



3. — Mixed with arsenious oxide, and heated in a hard glass tube, 



the characteristic garlic-like odour of cacodyl, was evolved, 



shewing the presence of an acetate. 



II. — The shells were broken into small pieces, and placed in a 



beaker of distilled water, the whole being left to macerate for a week. 



