48 MR « hatchett's experiments 



chemical examination ; it is not therefore furprifing, that the 

 opinions of chemifts concerning it have been various. Chaptal 

 adopts tlie opinion of GeofTroy, and calls it a kind of wax ; * 

 but Gren f and Fourcroy £ regard it as a true refin. 



§ I. 



Chemical Experiments on Lac. Its Habitudes with Solvents. 

 Water "ext rafts I. Water digefted upon powdered flick lac becomes of a 

 thecolour fiom deep crimfon colour, and takes up about 10 per cent. Seed 

 lac gives out no more than 2\ or 3 per cent, and (hell lac only 

 ^ i per cent, by fimilar treatment. 

 Alcohol diffolves 2. Alcohol diflblves much of the lac, taking up refin in a 

 the refin, which c]ear f j ut j on if co \^ . but if heated, the folution is turbid and 

 is a urge part. 



fcarcely to be rendered tranfparent, either by repofe or fil- 

 tration. 



The refin is obtained either by evaporating the folution or 

 by pouring it into water acidulated with muriatic or acetic acid. 

 The refin which is thus precipitated may be feparated by the 

 filter. It amounts to 61 or 68 per cent, in flick lac, and to 

 88 in the feed lac. Shell lac contains 81 per cent, befides 10 

 per cent, which is defended from the fpirit, and cannot be fe- 

 parated but by fubfequent operation. The refin is lefs brittle 

 than other refin. 

 Vegetable When the fhell lac was in fmall fragments only, thefe after 



S luten * the firll feparation of the refin, retained their figure and were 



more bulky, porous, and elafiic. The elafticity was deftroyed 

 by boiling water, and the matter itfelf proved to be of the na- 

 ture of vegetable gluten. 

 Ether affects lac 3. Sulphuric ether adts lefs powerfully on lac than alcohol 

 very little. does. It confiderably foftens the lac ; but produces little other 



effea. 

 Sulphuric acid 4. Concentrated fulphuric acid firfl a&s on the colouring 



coaT" 5 h mt ° matter > but after a (hort d 'g eftion on the fand bath > the fl uid 

 a£ts on the whole mafs, and becomes firft reddifli brown, and 

 afterwards black, fulphureous acid gas being evolved, and the 

 chief part of the lac being at length feparated in a ftate refem- 

 bling coal. 



* Chaptal's Elements ; Englilh edition.' Vol. III. p. 387. 

 f Principles of modern Chemiftry. Vol. I. p. 388. 

 X Syjihne des Connoiffanca chimiquts^ Tome V. p. 624. 



Nitric 



