LUTES. 306 



The coating us$d for retorts, &c. to defend 

 them from the action of the fire, is usually com- 

 posed of nearly equal parts of coarse sand and re- 

 fractory clay. These matters ought to be well 

 mixed with water and a little hair, so as to form 

 a liquid paste, with which the vessels are covered 

 layer upon layer, till it is of the required thick- 

 ness. The sand, mixed with the clay, is necessary 

 to prevent the cracks which are occasioned by the 

 contracting of the clay during its drying, which 

 it always does when pure. The hair serves also 

 to bind the parts of the lute, and to keep it ap- 

 plied to the vessel ; for, notwithstanding the sand 

 which is introduced into it, some cracks are al- 

 ways formed, which would occasion pieces of it to 

 fall off. 



The lutes with which the joinings of vessels are 

 closed are of different kinds, according to the nature 

 of the operations to be made, and of the substances 

 to be distilled in these vessels. 



When vapours of watery liquors, and such as are 

 not corrosive, are to be contained, it is sufficient to 

 surround the joining of the receiver to the nose of 

 the alembic, or of the retort, with slips of paper, oi- 

 lmen, covered with flour paste. In such cases, 

 also, slips of wet bladder are very conveniently 

 used. 



When more penetrating and dissolving vapours 

 are to be contained, a lute is to be employed of 

 quick-lime slacked in air, and beaten into a liquid 

 paste with whites of eggs. This paste is to be 

 spread upon linen slips, which are to be applied 

 exactly to the joining of the vessels. This lute is 

 very convenient, easily dries, becomes solid, and 

 sufficiently firm. 



VOL. II. X 



