100 Chemical Analysis of Caviar. [A us. 



think therefore it will be safer, in the present state of our know- 

 ledge, to deduce the weight of an atom of antimony from the sul- 

 phuret of that metal, with the composition of which we are accu- 

 rately acquainted, than from imperfect deductions respecting oxides 

 which have not hitherto been subjected to a satisfactory examina- 

 tion. 



Article V. 



Chemical Analysis of Caviar. By Professor Dr. John, of 

 Frankfort-on-the-Oder.* 



Caviar, as is known, is formed from the roe of some species of 

 fishes, especially some species of stufgzom, as the Accipenser sturio, 

 A. huso, A. rathenus. It comes in a two-fold state, from Russia 

 where it was probably prepared, f to us in Germany. Two kinds of 

 caviar are distinguished in commerce, namely, the pressed and 

 fresh caviar. Now this last kind, as it consists of the roes of the 

 fish unaltered (some sturgeons yield 200 pounds of this substance), 

 when it is subjected to analysis, will yield a result more to be de- 

 pended on than the pressed caviar, which is not only mixed with 

 foreign matter, as common salt, but which, by being dried and 

 subjected to pressure, has undergone a real change in its nature. 

 There is a good description of the method of preparing the pressed 

 caviar in Kriinitz' Encyclopedia. I employed in the following 

 analysis true Russian caviar, the roes of which had been pressed 

 together in consequence of the distant carriage, but which had 

 undergone no fermentation, nor any ether alteration. 



1 rubbed 4L'0 grains of this fresh caviar with water into a thin pap, 

 and then mixed it with a greater proportion of that liquid. I ob- 

 taineda solution similar to an emulsion, from which the membranous 

 part of the caviar gradually precipitated to the bottom of the vessel. 

 It was obvious from the appearance of the solution that it contained 

 an oily matter mixed with it. The whole was poured upon the 

 filter, through which there passed a pretty transparent and colour- 

 less solution. The residuum which remained upon the filter was 

 treated with water in the same manner as at first, by which the 

 dissolving power of the water seemed to be. exhausted. The solution 

 in water, being evaporated, coagulated, and deposited a white sub- 

 stance similar to the curdy part of milk. Alcohol, being dropped 

 into the liquid, contributed to the coagulation and precipitation of 

 this substance. This substance being separated by the filter, and 

 dried in a hot place, assumed the form of a transparent, brittle, 



* From the Geseh:c!iaft Nnturfor-chcnder frennde zu Berlin Magazine for 1810, 



p. 307. 



t Several other fish furni-h a substance similar to common caviar, and it is ure- 

 "parcd hi different purls -of Prussia and Pomerania. 



