June 14, 1918] 



SCIENCE 



593 



the isolatio7i and purification of pectin. The 

 studies, which were for the most part carried 

 on at the Washington Agricultural Experiment 

 Station, were at first concerned with the prep- 

 aration and concentration of pectin for house- 

 hold use.' This work led to attempts to de- 

 velop practical and inexpensive methods for the 

 isolation of pectin in a pure state which should 

 be equally available for the household or for 

 commercial use. Such a method was developed 

 and perfected in the autumn of 1917, but the 

 transfer of the authors from the Washington 

 Station to this office has delayed the prepara- 

 tion of a detailed report of the results for pub- 

 lication. The purpose of this preliminary 

 note is to make the method immediately avail- 

 able pending the publication of a detailed 

 paper now in the hands of the editor of the 

 Journal of Agricultural Research. 



The method is available for use with any 

 pectin-containing material, since the objection- 

 able flavoring substances of such materials as 

 carrots are entirely removed. 



The pectin is extracted from the material by 

 the usual method of pulping, boiling with 

 water and draining, this process being repeated 

 until the pulp is exhausted. The watery ex- 

 tracts are combined, cooled, and a small quan- 

 tity of a saturated solution of commercial 

 alum, the exact amount being determined by 

 the viscosity of the liquid, is slowly added and 

 thoroughly mixed with the solution. Ammonia 

 is now added in an amount slightly greater 

 than that necessary to neutralize the acidity 

 of the solution or until no further precipitate 

 is formed. Precipitation will not occur if the 

 solution is a concentrated, viscous one, and in 

 all cases warming, or preferably diluting with 

 hot water, hastens the coagulation of the pre- 

 cipitate and the clarification of the liquid. 

 The voluminous insoluble precipitate of alu- 

 minum hydrate holds and carries out with it 

 suspended solids and a considerable portion of 

 the coloring matter. 



As soon as the clarification is completed the 



1 Caldwell, J. S., " A New Method for the Prepa- 

 ration of Pectin," Wash. Agric. Expt. Sia. Bull, 

 147: 1-14, April, 1917. 



solution is filtered and the residue upon the 

 filter paper is preserved and dried for subse- 

 quent recovery of the aluminum. An ordinary 

 laboratory grade of filter paper permits rapid 

 filtration and retains the precipitate perfectly. 



The water-clear filtrate, which contains only 

 I)ectin, sugars, and traces of coloring matter, 

 is heated to boiling, and magnesium-sulphate 

 crystals are added, with constant stirring, 

 until the formation of the flaky, grayish pre- 

 cipitate of pectin has ceased. The solution is 

 then passed through filter-paper, preserving the 

 filtrate, and the precipitate is freed from mag- 

 nesium sulphate by washing with cold water 

 and dried. The dry preparation may be 

 readily reduced to a grayish powder, in- 

 soluble in cold water but readily soluble in 

 warm acid solutions. It is entirely free from 

 the coloring and flavoring matters of the 

 material from which prepared. It may con- 

 sequently be employed in making jellies from 

 even the most delicately flavored fruit juices 

 without danger of introducing foreign flavors. 

 This makes possible the use not only of fruits 

 but also of such pectin-rich but hitherto un- 

 available materials as the carrot as sources 

 of pectin for jelly-making purposes. By rea- 

 son of the purity of the product made by 

 this method, it may be kept for prolonged 

 periods in the dry condition without deteriora- 

 tion. In comparison with the ordinary com- 

 mercial concentrated pectin there is an enorm- 

 ous reduction in volume and in cost of storage 

 and transportation, a considerably decreased 

 cost of production with a wider variety of raw 

 materials available as .sources, and a greatly 

 increased range of usefulness. 



An especially valuable feature of the process 

 is that the chemicals employed may be almost 

 completely recovered, thus reducing the cost of 

 the process to a minimum. The aluminum 

 salt is recovered as aluminum oxide by incin- 

 erating the residue from the first filtration. 

 The magnesium sulphate is recovered as such 

 from the final filtrate by concentration and the 

 addition of a small quantity of alcohol, which 

 causes the prompt crystallization of the salt, 

 leaving coloring matters and sugars in solu- 

 tion in the dilute alcoholic liquid. Purifica- 



