K. DOMESTIC AND HOUSEHOLD ECONOMY. 475 



by roasting coffee to a light-brown color; but by continuing 

 the operation until the beans become almost black, a small 

 jDortion of caffeine escapes. On the other hand, the caffeine 

 "is more completely extracted from the dark-roasted beans, 

 and consequently an infusion from a given weight of them 

 will be somewhat richer in caffeine than that from the same 

 weight of lightly roasted. It seems, therefore, that it may 

 be left simply as a matter of individual taste as to the de- 

 gree to wiaich coffee should be roasted, and also as to whether 

 it should be extracted by percolation or boiling, since it was 

 also established that the caffeine passes almost entirely into 

 an infusion. By comparative tests of tea and coffee, after 

 preparing the extracts according to the usual household meth- 

 ods, the interesting fact was established that the amount of 

 caffeine in a cup of good coffee, prepared from 260 grains of 

 coffee, is the same as that in a cup of good tea prepared from 

 75 to 90 grains of Pekoe tea. It was also found that the other 

 extractive principles can, for the most part, also be obtained 

 by simple infusion, but that the amount obtainable in this 

 way from strongly roasted coffee is larger than that from 

 the slightly roasted, although the total amount, as ascertain- 

 ed by other methods, is the same in both kinds. In its phys- 

 iological effects upon mammalia and frogs, caffeine seemed 

 related to strychnine ; but the experiments seemed to render 

 it very questionable whether the physiological effects of cof- 

 fee are to be attributed solely, or even mainly, to the caffeine 

 present, since extract of coffee beans, free from caffeine, pro- 

 duced powerful effects on animals, and of a very different 

 character from those of caffeine. A comparative investiga- 

 tion of these effects is proposed by Aubert, in w^hich special 

 attention will be paid to the considerable amount of active 

 potash salts present in coffee. The experiments, up to this 

 point, offer no explanation of the invigorating effect to Avhich 

 coffee owes its popularity. 13 C, SepUmher 1, 1872, 1167. 



EXAMEL FOR COPPER COOKING VESSELS. 



To enamel the inside of copper cooking vessels in which 

 acid fruit and vegetables are cooked, and thus prevent the 

 formation of the so-called "verdigris," the following method 

 is recommended: Twelve parts of white fluor-spar, twelve 

 parts unburned gypsum, and one part borax are finely pow- 



