10 BULLETIN 1025, U. S. DEPARTMENT OF AGRICULTURE. 
ployed retain traces of salts even after very prolonged washing on 
a filter and can be purified only by dialysis. A portion of the ma- 
terial forms quite stable suspension in a fruit juice to which it is 
added, the precipitate forms very slowly, the removal of colloidal 
matter is imperfect, and the filtration of a juice so treated is almost 
impossible by reason of the prompt formation over the filtering 
surface of a slimy, well-nigh impervious layer. Silicic-acid gels pre- 
pared and purified by more exact methods also fail to give satisfac- 
tory clarification or to filter readily. The preparation of the gel in- 
volves too many difficulties, and its use yields results too far short 
of satisfaction to make it a promising material for use in clarifying 
fruit juices. 
DIATOMACEOUS EARTH (KIESELGUHR) AS A CLARIFYING AGENT. 
Diatomaceous (* infusorial”) earth (kieselguhr)? has been recom- 
mended as a filtering agent for various liquids, and patents covering 
its use in ceitine cane juices were issued in both Great Brean 
and the United States as early as 1886 (21, p. 586). Its use for the 
purpose, either alone or in combination with other materials, has 
been repeatedly suggested in the older literature. More recently 
there has been a decided revival of interest in kieseleuhr as a clarify- 
ing agent, as evidenced by a considerable number of papers and the 
patenting of several processes. Gore (12) recommended its use as 
an aid to the filtration of previously neutralized apple juice in making ~ 
apple sirup and also as an aid in filtering fresh apple juices through 
a filter press (77). More recently Peck and Adams (26) have de- 
scribed a new carbon intended for use in clarifying cane juices, which 
is made by mixing molasses with kieselguhr, treating with sulphuric 
acid, baking, and washing free of acid. The material is reported to 
have very great decolorizing power and to give very considerable in- 
crease in purity with a reduction of gums to 30 to 45 per cent of the 
amounts present before treatment, which would suggest, in view of 
Zerban’s results with carbons, that the ele aids very ma- 
terially in the adsorption of gums. 
Peck (24). has reported results obtained by the addition of kiesel- 
guhr to the juice at the rate of 5 pounds per ton of cane, with con- 
siderable increase in purity. The same author in an address has 
also made incidental mention (25) of the work of Walter L. Jordan 
in filtering juices through kieselguhr, stating that an increase in 
purity was obtained, but Peck gives neither details nor citation of 
Jordan’s paper, which it has been impossible to locate in the litera- 
? Since kieselguhr consists chiefly or wholly of the siliceous frustules of diatoms, it 
is unfortunate that the older and correct designations diatomaceous earth, diatomite, or 
tripolite, which suggest the origin and chemical character of the material, should have 
been replaced in trade usage by the wholly misleading term ‘‘infusorial earth.” 
