120 NOTE ON THE PREPARATION OF 



Another point that requires attention arises from the fact that the P. B. 

 solution of sulphurous acid, as obtained from the chemist, is generally some- 

 what deficient in the amount of SOo, in consequence of loss by volatilization. 

 Hence it is necessary to use a smaller quantity of water for dissolving the chromic 

 acid than would otherwise be used ; and when the proper tint has been got, 

 add enough distilled water to bring the liquid to the requisite measure. 



The following directions for preparing what is known as chromic (or some- 

 times sulpho-chromic) catgut in accordance with the above conditions were 

 given to manufacturing chemists in 1894, but have never yet been published :— 



' The preparing liquid must be twenty times the weight of the catgut. 

 So for 40 grains of catgut 800 grains of preparing liquid are required. It is 

 made by mixing two Hquids — nameh', the chromium sulphate liquid and the 

 sublimate liquid. 



' The sublimate liquid is : — 



Corrosive sublimate . . . . .2 grains 

 Distilled water ..... 320 ,, 



'The sublimate^ may be dissolved by heat, but the solution must be 

 used cold. 



' The chromium sulphate liquid is prepared thus : — 



Chromic acid ...... 4 grains 



Distilled water ...... 240 ,, 



' Add to this as much sulphurous acid {P.B. solution) as gives a green 

 colour. If more is added the colour becomes blue, which shows that rather 

 too much sulphurous acid has been used. It is well to reserve a few drops of 

 the chromic-acid solution, to be added after the blue colour has just appeared 

 and restore it to green. Then enough distilled water is added to bring the 

 green liquid up to 480 grains. Then add the sublimate liquid.' 



The catgut is kept twenty-four hours in the preparing liquid, and is then 

 dried on the stretch. 



N.B. — It is essential that the CrOs and SOo solutions be mixed before the 

 HgCh solution is added. 



Catgut prepared in this wa\' remains activeh' antiseptic in its substance for 

 an indefinite period, as was shown by the following experiment : — 



Some slender hanks prepared three years previously, weighing 207 grains, 

 chopped into short segments, were placed in a small mortar and treated with 

 enough distilled water to cover them, 2,000 grains being required for the purpose. 

 The gut was then pressed firmh- with a pestle, and the same was afterwards 

 done three times at intervals of about three hours. The gut and water were 



