774 GUTTA-PERCHA 



appear to attack gutta-percha when cold ; when hot, it dissolves a small portion of it, 

 which is again precipitated on cooling. 



Sulphuric acid with one equiv. of water colours it brown, and disintegrates it with a 

 sensible evolution of sulphurous acid. 



Muriatic acid, in its saturated solution in water at a temperature of 68 F., attacks 

 gutta-percha slowly, and gives it a more or less deep brown colour, at length rendering 

 it brittle. 



Monohydrated nitric acid attacks it rapidly, with effervescence and an abundant 

 evolution of fumes of hyponitrous acid ; the substance is decomposed, and coloured of 

 a brownish orange-red : it becomes doughy, and afterwards solidifies by degrees and 

 remains friable. 



In the cold, and even by heat, only a part of the gutta-percha (0'15 to 0-22) is dis- 

 solved by anhydrous alcohol or other. Benzine and spirits of turpentine dissolve it 

 partially when cold, but nearly completely if aided by heat. Sulphide of carbon and 

 chloroform dissolve gutta-percha when cold ; the solutions may be filtered beneath a 

 bell-glass to prevent evaporation ; the filter retains the foreign matters of a reddish 

 brown colour, whilst the solution passes perfectly clear, and almost colourless. The 

 filtered liquid, exposed to the air in a saucer, allows the solvent to escape, and deposits 

 the white gutta-percha in a plate of greater or less thickness, which shrinks gradually 

 in proportion to the evaporation of the liquid. 



Except the colour, which has disappeared, the gutta-percha then offers the characters 

 and properties mentioned above as belonging to the commercial substance. Submitted 

 to a gradually-raised temperature, it softens and melts, and may be made to boil with- 

 out acquiring a sensible colour ; the transparent fluid gives off abundant vapours, which 

 are condensible into a nearly colourless oily liquid. The portions last distilled have a 

 brownish orange colour, and a thin layer of carbonaceous deposit remains adherent to 

 the sides of the vessel. 



Analysis. We have said above that alcohol and ether can dissolve only a portion of 

 gutta-percha ; this is because that substance consists, in fact, of three proximate prin- 

 ciples, the separation of which has required very delicate observation, although they 

 are very clearly distinguished by several of their properties. 



When gutta-percha in thin leaves is brought into contact, in a close vessel, with 15 

 to 20 vols. of cold anhydrous alcohol, and the temperature raised slowly by means of 

 the water-bath to the point of ebullition (172 F.), and kept at this point during 

 several hours, the liquid, if filtered whilst boiling and left in a closed flask, will, at the 

 end of from 12 to 36 hours, begin to deposit on the sides of the vessel and on the sur- 

 face of the solution white opaline granules, distant from one another, but some of them 

 in groups ; their size will gradually increase for some days. These granules, carefully 

 examined under the microscope, will be found to have the form of spherules truncated 

 by the sides of the vessel. Their surface is either smooth, or bristling with very small 

 transparent, elongated, lamellar crystals. Some superficial fissures appear to indicate 

 that these spherules are formed of a sort of transparent yellow kernel covered with a 

 white pellicle. 



Perhaps no other example is known of this singular crystalline structure. In fact, 

 cold anhydrous alcohol dissolves the whole of the yellow spheroidal substance, whilst 

 the superficial pellicle, in the interior of which the alcohol has substituted itself for 

 the solid globule, appears whiter and less transparent. 



The alcoholic solution, which has been for some days depositing this complex sphe- 

 roidal crystallisation, can again take up by heat a portion of the two proximate prin- 

 ciples remaining in the substance, allowing a fresli quantity to crystallise on cooling. 

 The extraction is completed by returning the boiling alcohol several times upon the 

 gutta-percha until it no longer dissolves anything. 



The solid substance which has resisted the action of the solvent, possesses, with 

 some modifications, the principal properties of crude gutta-percha; wo shall hero 

 call it pure gutta. As to the two other organic principles, one is a yellow resin, which 

 is much more soluble in cold alcohol than the other, the white crystalline r>.-iii. 



By taking advantage of these different degrees of solubility, wo are enaMed with 

 time and patience to effect the complete purification of these three principles. The 

 separation may also be effected by treating finely-divided gutta-percha with cold ether, 

 which dissolves the mixture of the two resins more abundantly than alcohol ; ' 

 afterwards separated from one another by tho same treatment already dorribcd for 

 alcohol. 



The tendency of the white resin to form itself into radiated groups is manifested in 

 a rather remarkable circumstance, which it is easy to reproduce. Narrow ril>amls 

 cut from a thin leaf of ordinary gutta-percha are to bo placed in a tu!>o, and immersed 

 in anhydrous alcohol. The tube is then closed, and left for twenty or thir 

 when a few whitish points appear here and there on the ribands, and afterwards on 



