CHEMICAL SCIENCE. 257 



residual coffee made, to which the same oils might be afterward added, giving 

 a good portable coiTee. This attempt was also unsuccessful. 



It was next tried to obtain a portable coffee by making an aqueous extract 

 of raw coffee, evaporating to dryness, and roasting the residue. An extract 

 was obtained that, under some circumstances, gave good coffee, but as a whole 

 the results were not satisfactory. 



An experiment was also made to ascertain whether a very concentrated 

 aqueous solution of coffee could not be made from ground roasted coffee by 

 displacement with cold water, thus extracting more soluble matter than is 

 done hi the household, and at the same time obtaining a more portable coffee. 

 A pound of ground roasted coffee was placed in each one of a series of five 

 displacement apparatus, and river water poured through them, a pint at a 

 tune, using that which had run through the first to pour upon the second, 

 and so on through the series. The coffee swelled, and each pound absorbed 

 a quart of water during the swelling, which it did not suffer to drop, but which 

 was displaced by fresh water. As soon as a quart and a half had been passed 

 through one of the series, the absorbed liquid remaining in the coffee waa 

 pressed out by an hydraulic press of nine tons' power, and the droppings 

 added to the following numbers in the series, which were treated in a similar 

 way. By this means a very concentrated liquid was obtained. There were 

 in all 24 pints of water added, and the resulting portions of coffee solution 

 amounted altogether to about 18 pints, from which it follows that, notwith- 

 standing the powerful pressure, the coffee residue retained six pints of water, 

 or 11 th its weight. When this coffee residue was dried, it was much lighter 

 in color than ordinary coffee, and a cup of infusion, made in the ordinary way, 

 had not the slightest flavor of coffee, and resembled in taste the decoction 

 that one is served with hi country taverns in the interior of Pennsylvania. 



Those articles offered in the market under the name of "extract of coffee," 

 and which profess to enable one by adding them to ground coffee to save in 

 the preparation of the beverage, are all worthless and catch-pennies. They 

 contain burned sugar, chickory, carrots, sometimes coffee, and other materials, 

 aad act only by giving a dark color to the infusion, and a peculiar taste, 

 which misleads persons to think that the coffee made by their aid is stronger. 

 The excellence of coffee as a beverage depends upon its caffein and a peculiar 

 volatile oil, which are not contained in the above-mentioned additions. As 

 early as 1TS2, one of these coffee essences was analyzed, and found to contain 

 au alkaline carbonate ; and it has been lately proposed to add carbonate of 

 soda to the ground roasted berry in the proportion of 43 grains of the former 

 to a pound of the latter, but it may be questioned whether this is a valuable 

 addition, as Bohmes observed that a small quantity was useless, while a 

 larger quantity communicated an unpleasant taste to the coffee. Journal 

 Franklin Institute. 



CURIOUS CHE3IICAX CHANGES OBSERVED IX CERTAIN WATERS. 



The following paper was recently communicated to the Boston Society of 

 Natural History, by Dr. A. A. Hayes : 



