SCIENCE IN SHORT CHAPTERS. 



the oft-repeated and contradicted statement that copper is used in 

 coloring green tea. One of the essential ingredients in the manufact- 

 ure of Prussian blue is sulphate of iron, the common commercial 

 name of which is ' green copperas.' It is often supposed to con- 

 tain copper, but this is not the case. 



" Your Shanghai correspondent overrates the market value of soap- 

 stone when he supposes that Chinese wax may be used as a cheap 

 substitute. In many places as, for instance, the ' Lizard ' district 

 of Cornwall great veins of this mineral occur, which, if needed, 

 might be quarried in vast abundance, and at very little cost on 

 account of its softness. The romantic scenery of Kynance Cove, its 

 caverns, its natural arches, the ' Devil's Bellows,' the ' Devil's 

 Post-Office,' the 'Devil's Cauldrons,' and other fantastic forma- 

 tions of this part of the coast, attributed to his Satanic Majesty or 

 the Druids, are the natural results of the waves beating away the 

 veins of soft soapstone, and leaving the deformed skeleton rocks of 

 harder serpentine behind. ' ' 



CHAPTER XXXI. 



'IKON FILINGS" IN TEA. 



1 HAVE watched the progress of the tea controversy and the other 

 public performances of the public analysts with considerable inter- 

 est ; it might have been with amusement, but for the melancholy 

 degradation of chemical science which they involve. 



Among the absurdities and exaggerations which for some years 

 past have been so industriously trumpeted forth by the pseudo- 

 chemists who trade upon the adulteration panic and consequent de- 

 mand for chemical certificates of purity, the continually repeated 

 statements concerning the use of iron filings as a fraudulent adulter- 

 ant of tea takes a' prominent place. I need scarcely remark that, in 

 order to form such an adulterant, the quantity added must be suffi- 

 ciently great to render its addition commercially profitable to an 

 extent commensurate with the trouble involved. 



The gentlemen who, since the passing of the Adulteration Act, 

 have by some kind of inspiration suddenly become full-blown chem- 

 ists, have certified to wilful adulteration of tea with iron filings, and 

 have obtained convictions en such certificates, when, according to 

 their own statement, the quantity contained has not exceeded 5 per 

 cent, in the cheapest qualities of tea. Now, the price of such tea to 

 the Chinaman tea-grower, who is supposed to add these iron filings, 

 is about fourpence to sixpence per pound ; and we are asked to be- 

 lieve that he will fraudulently deteriorate the market value of his 

 commodity for the sake of this additional l-20th of weight. Suppos- 

 ing that he could obtain his iron filings at twopence per pound, his 

 total gain would thus be about l-10th of a penny per pound. But 

 can he obtain such iron filings in the quantity required at such a 

 price ? A little reflection on a few figures will render it evident that 

 he cannot, and that such adulteration is utterly impossible. 



