34 SUBSTANCES SOLUBLE IN ETHER. 



last-named solvents (prepared warm if necessary) should be 

 resorted to in the attempt to crystallize the substance, or to 

 separate it into a crystalline and an amorphous portion. 



If the endeavour^to obtain crystals be successful, the crystalline 

 form should if possible be determined, and care should be taken 

 to observe whether different crystalline forms can be distinguished 

 under the microscope, rendering it probable that the substance-- 

 under examination is a mixture. l 



41. Behaviour of Eesins to Reagents. It will further be of 

 special interest to learn whether the substances soluble in ether,, 

 insoluble in alcohol and water, are dissolved by alcoholic or 

 aqueous solution of caustic potash, in which case there would be 

 reason to suspect the presence of an acid resin ( 145). If in- 

 soluble in these liquids it might be assumed that the body 

 under examination is an indifferent resin, or a resin-anhydride not 

 easily susceptible of decomposition. These and the following 

 experiments should be conducted with larger quantities of the 1 

 substance soluble in ether, specially prepared for this purpose. 



If an indifferent resin or stable resin-anhydride were present it 

 might first be purified by recrystallization or reprecipitation, etc., 

 and then an ultimate analysis made. It should be tested for 

 colour-reactioHS with concentrated sulphuric acid alone and in 

 conjunction with sugar. If ethereal solution of bromine yield & 

 substitution product, its composition should be ascertained. It 

 should also be noticed whether the resin-anhydride is easily 

 oxidized and dissolved by nitric acid, or whether that takes place- 

 only with difficulty j whether water precipitates the unchanged 

 resin after the action of the acid, or whether oxidation products 

 are formed ; and if so, what is their nature, as, for instance, picric 2 

 or oxalic acid ( 81, 219), succinic acid ( 220). 



42. Action of Fused Potash. It is further important to become 

 acquainted with the products formed under the influence of fused 

 caustic potash or soda. 3 The finely powdered substance, in quan- 



1 For particulars of a case of this kind, viz. the separation of a mixture of 

 resins obtained from larch-fungus, see Masing, Pharm. Zeitschr. f. Russland, 

 Jg. 9, p. 394 (1870). 



2 Bitter yellow crystals belonging to the rhombic system sparingly soluble in 

 cold water, more freely in boiling, soluble in alcohol and ether. It stains skin 

 and wool yellow, and yields a blood-red liquid when an alkaline solution is 

 warmed with cyanide of potassium, sulphide of potassium, or grape sugar. 



3 Cf. Hlasiwetz and Earth, Annalen der Chemie und Pharm. cxxxiv. 265 ' r 

 cxxxviii. 61 : cxxxix. 77. 



