COL LIN. 203 



Dry gelatin undergoes no change when kept ; but in the ge- 

 latinous state, or when dissolved in water, it very soon putrefies ; 

 an acid makes its appearance in the first place (probably the 

 acetic,) a fetid odour is exhaled, and afterwards ammonia is 

 formed. 



When dry gelatin is exposed to heat, it whitens, curls up like 

 horn, then blackens, and gradually consumes to a coal ; but tre- 

 mulous gelatin first melts, assuming a black colour. When dis- 

 tilled, it yields, like most animal substances, a watery liquid im- 

 pregnated with ammonia, and a fetid empyreumatic oil ; leaving 

 a bulky charcoal of difficult incineration. It is by no means a 

 very combustible substance. 



Collin is not sensibly soluble in alcohol,* and when alcohol is 

 poured into a warm concentrated solution, the whole gelatin coa- 

 gulates into a white, coherent, elastic, and fibrous mass, which 

 adheres strongly to glass, and gelatinizes in cold water, without 

 dissolving. Collin is likewise insoluble in ether and in oils both 

 fixed and volatile. 



When a current of chlorine gas is passed through a solution 

 of gelatin in water, a white solid matter collects on the surface, 

 and whitish filaments swim through the liquid. This solid mat- 

 ter, when separated by the filter and purified, possesses the fol- 

 lowing properties ; its colour is white ; it is specifically lighter 

 than water ; it has little or no taste ; when dried in the open air 

 it falls to powder ; it is not soluble in boiling water ; it dissolves 

 in hot nitric and acetic acids, but precipitates again as the solu- 

 tion cools ; when triturated with potash it emits the smell of am- 

 monia ; it does not affect vegetable blues.f Bouillon La Grange, 

 to whom we are indebted for these facts, has given the gelatin 

 thus altered the name of oxygenized gelatin. It has been recently 

 examined by M. Mulder.J 



When a current of chlorine gas is passed through a solution 

 of isinglass in lukewarm water, no change is apparent at first. 

 But in two or three minutes each bubble becomes surrounded 

 with a white substance, which adheres gradually to the sides of 

 the vessel as a white, elastic, and very cohesive substance. This 



* Isinglass dissolves very well in rectified spirits. This property, together 

 with want of colour, distinguishes it from common collin. 

 f Bouillon La Grange, Nicholson's Jour. xiii. 209. 

 \ An", der Pharm. xxxi. 332. 



