430 PHILOSOPHICAL TRANSACTIONS. [aNNO 1794. 



meter. In boiling water it readily melted, and the black exuviae were thus sepa- 

 rated from the lac. Two thousand grains of white lac were exposed in 

 such a degree of caloric* as was just sufficient to melt them ; as they 

 became soft and fluid, a pretty large quantity of reddish watery fluid, namely 

 550 grs., which emitted the smell of newly baked bread, oozed out. This 

 liquid was poured off for examination, and the lac was strained through 

 fine cloth repeatedly, till it left no exuviae or other extraneous matter 

 on the filter. The quantity of purified lac' thus obtained was 1220 grs. It was 

 yellow like bees-wax ; hard and brittle as rosin. It had no bitterish or scarcely 

 any other taste. It melted in alcohol, and also in water, of the temperature of 

 between 145° and 146°. Purified white lac adheres very firmly to wood, tin, 

 paper. &c. so that it is an excellent cement on many occasions. 



3. Experiwenls to discover some of the affinities and combination of white lac. — 

 1, Yellow purified lac above-mentioned was spread thin on a plate of glass, and 

 exposed to the rays of the sun during the whole of the month of July, 1793, 

 but it was not by this means rendered at all less yellow. 2. A bit of white lac, 

 on boiling in water with powdered charcoal was absorbed, and disappeared. 3. 

 Purified lac was digested in various proportions of ley of pure pot-ash, in different 

 temperatures, but a uniform or soap-like mass could not be formed. The mixture 

 emitted the smell of palm oil. The lac turned to a brown colour, and had the 

 appearance of a coagulated mass, in the liquid as well as dry state. The liquid 

 filtered from these solutions had a sweetish and bitterish taste. On the addition 

 of vinegar, it became very turbid and rose-coloured ; and by standing it let fall a 

 copious sediment, which being dried was found to be white lac only rendered 

 more brittle. 4. Ammoniac, or caustic volatile alkali seemed to combine with 

 the white lac. The compound was a tolerably uniform brown soapy substance. 

 It tasted sweet, and had still a weak smell of ammoniac. It rendered water 

 milky, and this solution became curdy on adding to it acetous acid. 



5. Candles, of different thicknesses, were made of purified white lac above- 

 mentioned, with cotton wicks of different thicknesses ; and candles were also 

 made of white lac which had been dissolved in sulphuric ether, and in volatile oil 

 of turpentine. They all burned more rapidly, but I think emitted a less quan- 

 tity of light, than wax candles, of the same size. The candles made of white 

 lac also smoked and produced a resinous smell. White lac burned In oxygen 

 gaz without affording any smoke, and with a beautifully bright flame. A small 

 piece of purified white lac, in a platina spoon, was exposed to the apex of the 

 violet blue coloured flame of a candle, by means of a blow-pipe; a small quan- 

 tity of black matter remained in the spoon, which could not be carried off by a 

 long continued application of the flame ; but after keeping the spoon red-hot 

 in the fire for 10 minutes, nothing but a very small quantity of grey ash was left. 



* The names of tlie new system of chemistry are employed in this paper, for which it is pre- 

 sumed a particular explanation is unnecessary, as its nomenclatiure is now very generally used. — Orig. 



