700 ■ 



latex (our 337,%) sliowed liiin the iransitioii from coagulated to 

 [)appy, liiil did not show distinctly, that he had got again into the 

 second liquid range (lines 3 and 4). Eaton did not observe the upper 

 range of coagulation. 



Whitby made a complete series at about 30 7o 'atex ; his limits 

 do not fully coincide with ours, which for the reasons already men- 

 tioned (own acidity latex etc.) is not astonishing, and also may be 

 (caused by wrong reproduction, as Whitby does not mention the 

 exact (itre of his hydrochloric acid. So except small differences the 

 observations of both investigators fit satisfactorily in the frame of 

 our recapitulating-figure (see fig. 6 and 2). 



2. N'itjic acid. Eaton made two series of observations, starling 

 from undilated latex, and always found coagulation at increasing 

 acidity, corresponding with Fig. 3. Moreover a series with 17, acid 

 with 1 : 2 diluted latex, with which lie passed from the range of 

 coagulation into a papjiy range ("incomplete coagulation"), which 

 again he attributes to the above mentioned causes (inclusion of acid 

 in the lumps). 



Whitby also described for nitric acid a ootnplete series, viz. for 

 a latex with 12 ° '„ rubber (corresponding with a mixture with 407« 

 latex); he found at 0.016 N coagulation, at 0.021 a pap, at 0.032 

 ;ui(l 0.052 liquid mixtures, al 0.063 a pap again, at 0.105 and 0.21 

 coagulation. These observations tally with ours (see Fig. 3), except 

 both the liquid mixtures (Whitby only says "coagulation failed to 

 occur", which possibly may correspond with our mixtures with a 

 little curdling). 



3. Sulphuric acid. Eaton made a series with undiluted latex, which 

 (as might be expected) showed coagulation at all acidities ; moreover 

 one with latex diluted 1 : 3 where after the range of coagulation 

 came a few mixtures with incomplete coagulation, and a series with 

 latex diluted 1 :10, where i-oagulated — incompletely coagulated — liquid 

 was stated. The fact of remaining liquid is attributed again by Eaton 

 10 a retardation of the coagulation with strongly diluted latex, but 

 he does not explain in which way he accounts for (he coagulated 

 mixtures with less acid found in this series. 



Whitby only gives a short indication about a series liquid — coagu- 

 lated — incompletely coagulated (pap) — coagulated, without mentioning 

 the percentages of acid and the percentage of rubber. Probably this 

 has been the same diluted latex with 10 7, I'nbber (30 7, latex) as 

 in his experiments with hydrochloric acid, and therefore Whitby 

 probably remained at a concentration, up to which the liquid range 

 does not reach, fcf. Fig. 4). 



