On extra^lng Gum from the Lichen, 229 



during four or five hours, adding about half an ounce or three quarters of an ounce of foda 

 or pearl afhes for every pound of lichen ; or, inftead of thefe falls, about half an Englifh ' 

 pint of volatile alkali. The boiling (hould be continued until the liquor acquires a con- 

 fiderable degree of gummy confidence. It is then to be taken out of the boiler, allowed to 

 drain or drip through a wire or hair cloth, or fearfe. The refiduum to be put info a hair 

 cloth bag or bags, and to be fqueezed in a prefs (imilar to that which is ufed by the melters 

 or rinders of tallow. 



The firft boiling does not extra(3: the whole of the gum. The lichen (hould be boiled 

 a fecond and even a third time, repeating the procefs as above defcribed, diminifhing at 

 each procefs the quantity of, water and the quantity of alkali, which a little experience wilL 

 foon point out. When three boilings are employed, the gummy extra£l of the lafl boiling 

 ihould be kept for the firft boiling of a frefli batch of lichen. The extraft proceeding from 

 the firft and fecond boilings (hould be mixed together, and evaporated to the confiftenci 

 neceffary for block or prefs printing. The evaporating velTels (houid be of tin or thin lead 

 placed over a range of ftoves and moderately heated by fire or the fteam of water. It has 

 been negle£ted to ftate, that before evaporating the gummy extrafl to the confiftence 

 necelFary, it (hould be kept ten or twelve hours, fo as to allow the fediment or dregs to 

 fubfide. The clear liquor miy either be drawn off by a fyphon, or thfe dregs may be drawn 

 off by a cock at the bottom of the wooden vefTel ; the bottom of which fliould be made 

 floping, higher at the back than the fore part, in order that the dregs may run more comr 

 pletely off. The proportion of gummy matter remaining in the dregs may be got off by' 

 mixing them with a due proportion of boiling water, allowing the liquor to clear, and 

 proceeding as above directed, employing this weak foluuon for boiling the next batch, 

 of lichen. 



The refiduum of the lichen, after the third boiling, confifts of a matter fomewhat 

 analogous to that of animal matter, together with a proportion of the fibrous matter 

 of the plant. From the animal matter a kind of foap may be made. The procefs is as 

 follows : 



Let a fmall proportion of pounded rofin be diffolved by boiling in a folution of alkaline 

 falts. When the rofin is diffolved, put in a certain quantity of the refiduum of the lichen j 

 and continue the boiling until this laft article is pretty well diffolved. Then add about a 

 pound or a pound and a half of white foap (haved down or cut into thin flices to every ten 

 pound weight of the refiduum of the lichen. Continue the boiling until the white foap is 

 fully diffolved. Then pafs the foapy folution through a hair fieve or hair bag. Let the 

 foap pan then.be cleaned out and the foapy folutionreturned to the pan, to be boiled to the 

 confiftence neceffary. A kind of foap very fimilar to this may be made from fea weed, as 

 well as from feveral other articles. Of this and of other matters, highly invportant to calico 

 printers,, a more full and detailed account will be given in a future publication, Whea 

 gum from the, lichen is to be employed for making ink, manufaftujcing and.ftaiuing papen 



' ao(L 



