©tt THE rROCESSES FOR CLARIFYING LIQUIDS. 231 



The white colour of the papier Jofeph fhews that it has been 

 manufactured with a fuperior material to that ufed for the 

 grey paper. The fluids which have parted through it are al- 

 ways very tranfparent, but it has the inconvenience of being 

 eafily torn, and its pores are foon obftrucled, fo that its filtra^ 

 tion is not effected with difpatch. 



The grey paper may be ufed for a long time alfo in pro- and their ufe«, 

 ducing clear fluids. But as the pafte out of which it was 

 fabricated was not as pure as that of the papier Jofeph, it al- 

 ways communicates a difagreeable tafte to the fluids, owing 

 to the folution of the foreign matters it contains. On this 

 account precifely it is that certain fluids, fuch as whey, wine, 

 ratifia, and other liquids for beverage, when filtered through 

 the grey paper, have always an odour and tafte, which deli- 

 cate organs foon recognize. And hence it is that among thofe 

 fluids fome of them are more fufceptible of alteration than 

 when they have been filtered through the papier Jofeph. 



The nature of the paper requires more particularly to be 

 confidered when faline folutions are to be filtered. If the 

 grey paper be ufed, it frequently happens that part of its 

 fubftance is diflblved by the faline liquor, fo that it becomes 

 lefs pure than before. This inconvenience, which is not fo 

 perceptible when the papier Jofeph is ufed, may be flill fur* 

 ther diminiihed, by ufing the precaution of employing fuch 

 filters only as have been previoufly waflied by repeated filtra- 

 tion of boiling water. The exa6t pharmacian ought to be al- 

 ways provided with filters thus wafhed, in order to have re- 

 courfe to them upon occafion. Joffe, fo diftinguifhed in 

 pharmacy, and to whom we are indebted for many important 

 obfervations, has found the advantage of thefe inftruments 

 under a multitude of circumftances. He has, among other 

 obfervations, remarked, that whey clarified and filtered through 

 (du papier raifin) may be kept for more than fifteen days, 

 by filtering it daily, which could not be done if it had been 

 filtered through the common grey paper, even though previa 

 oufly wafhed. 



By an effect direclly contrary to this, different juices and 

 plants are preferved tranfparent, and in good condition, with? 

 out parting to the acid ftate, in confequence of their having 

 been daily filtered through the grey paper. It was obferved 

 merely that their colour became more intenfe on the firfl days, 

 and that they afterwards became infenfiWy difcoloured. 



But 



