ILLUMINATING GAS. 165 



mass, soluble in alcohol of .863, but insoluble in water and cold 

 ether. 



3. Santalide, extracted by water ; a dark-red mass, soluble 

 in ether and alcohol of .863, but, when pure, insoluble in 

 water. 



4. Santaloide, extracted by water ; a yellowish amorphous 

 mass, soluble in cold water and alcohol of .863, but insoluble 

 in ether. 



5. Santaloidide, extracted by water ; a dark-brown resinous 

 mass, insoluble in water and ether, and only slightly so in cold 

 alcohol. 



6. Santalidide, extracted by water ; an amorphous brown 

 mass, soluble in water, sparingly so in boiling alcohol of .912, 

 and insoluble in ether and cold absolute alcohol. 



3. Illumination. 



The fatty bodies and resins of the preceding and present 

 classes, together with bituminous coals, are the sources of ar- 

 tificial light. The fats are generally used as oils, spermaceti 

 oil, whale oil, to be burned in lamps ; or the more fluid por- 

 tions of fat, as lard oil, are removed by pressure, and the hard 

 stearin remaining is formed into candles ; or a stearic fat is 

 decomposed by alkali and acid, so that stearic acid is obtained 

 to be made into candles. Spermaceti and wax are also burned 

 in the form of candles. Their preparation falls under a pre- 

 ceding division, while under the present we might consider their 

 comparative merits as sources of light ; as there is, however, 

 little of novelty to offer in this respect, we confine ourselves 

 to improvements in the gas manufacture, and to what are 

 termed burning-fluids. 



1. Illuminating gas is obtained by throwing bituminous 

 coal, grease, or rosin, upon a red-hot surface, whereby it is 

 resolved into new compounds by an internal combustion ; into 

 permanent gases ; vapors, which condense into aqueous solu- 

 tions and tar; and coke, which remains. The coke is used as 

 fuel ; the tar is either distilled to obtain ethereal oils and 



