270 APPARATUS FOR fRUSSIAN SLUE^ 



liquor in the tub. Two others pour the prussic liquor gently 

 into the funnel d, and the workman who holds the beater moves 

 it in all directions, that the liquors may be intimately mixed. A 

 little of the mixture is drawn off occasionally by the cock i, 

 filtered through blotting paper, and examined, to find whether 

 a sufficient quantity of prussiate of potash have been poured in : 

 if not, more is added ; and, v/hen it has reached the point of 

 saturation, no farther addition is to be made, but the stirring 

 of the mixture with the beater is to be continued about ten 

 minutes. 



The ash-pit of the furnace being closed, the draught of the fire 

 causes the outer air to enter through the tube of the funnel c?j 

 this air mixes with the gasses extricated from the mixture, and 

 the whole is conveyed through the tube e m underneath the 

 grate of the furnace, where the sulphuretted hidrogen takes 

 fire, loses thus its offensive smell, and serves also to keep up the 

 heat of the crucible. 



When the stirring of the mixture is finished, the tub may 

 be emptied by the cock_, and a new mixture immediately com- 

 ' menced. 



The cover of the tub need not be taken off, except when 

 the apparatus wants repair. When it is left some time out of 

 use, the tub should be kept; full of water, and this water may 

 be employed afterward for lixiviating the residuum of the calci- 

 nation of the blood and potash. 

 It has been The apparatus here described and figured I have caused to be 



employed w;th ^^^q^ ^p ^j- t^g paper-hanging manufactory of the brothers Jac- 

 -success. ^^''^ f, ,,. - , 



quemart. It has succeeded completely, no uiconvenience has 



been found in its use, and it has entirely freed the work-shops 

 and neighbourhood from the bad smell diffused by mixing the 

 prussic liquor, and the solution of alum and sulphate of iron. 



Note of the French Editors. 



A similar ap- An apparatus of this kind, but by no means so well con- 

 paratus atano- structed, has also been employed with success for several years 

 iher manufac- . . .- ,-* ■ ■ , • o ^t i i 



.<jfy.^ in a manufi\ctory of Prussian blue m St. Nicholas-street. 



V. 



