met 0.| with the State of Aggregation of Matter. 97 
extension and application of those which had been obtained some years 
before by Schiff.* 
It was noticed that when formaldehyde was added to Witte’s peptone, 
and the reaction mixture was then titrated by the Sodrensen method, the 
same amount of alkali was required for neutralisation both in the presence and 
absence of salts, 7.c. whether the precipitate was formed or not. In both 
cases, therefore, the formaldehyde had entered into reaction with the amino-- 
groups in the peptone. A clue to the nature of the phenomenon was 
afforded, however, by Schiff’s observation that asparagine, when treated 
with formaldehyde, yields a methyleneimino-derivative, which readily 
undergoes polymerisation or condensation in which more than one molecule 
takes part, with the formation of a complex insoluble compound.t It was 
therefore conceivable that certain constituents of Witte’s peptone react in a 
similar way, and the experiments recorded in the succeeding communication 
indicate that the precipitate is formed from the most complex polypeptide 
constituents of the peptone. If these be sufficiently complex as to be of 
colloidal nature, and to yield a solution which acts as a heterogeneous 
system, it is conceivable that adsorption of salts takes place on the surface of 
the colloidal molecules, and thus, by a kind of sterical inhibition, prevents 
the reaction of the large molecules with one another, to form, in the case 
under consideration, highly complex polymers.} 
The inhibitory action of salts on the polymerisation or condensation of the 
methyleneimino compounds was studied quantitatively in some detail (see 
succeeding paper), and found to agree very closely (with certain exceptions, 
which can be readily explained) with their inhibitory action on the 
formation of the zinc protein compounds which are produced when zinc 
sulphate is added in small quantities to protein solutions.§ 
During the course of these investigations it was also noticed that a marked 
parallelism existed between the inhibitory action of salts on the formation 
* Liebig’s ‘ Annalen,’ 1901, vol. 319, p. 287. 
+ Liebig’s ‘ Annalen,’ 1899, vol. 310, p. 25. 
{ Instances of sterical hindrance of reaction by atoms or groups combined in a 
molecule are, of course, well-known in the chemistry of simpler organic compounds, and 
are dealt with in detail in text-books on stereochemistry. (Cf. Stewart, ‘Stereo- 
chemistry,’ pp. 314-443. 
§ The conditions of the reaction between zinc sulphate and protein solutions are 
somewhat complex and have been studied by Pauli (Hofmeister’s ‘ Beitraége zur Physiol. 
u. Pathol. Chem.,’ 1905, vol. 6, p. 233). He found that when egg-white solution of a given 
strength was mixed with zinc sulphate solution of varying concentrations, two maxima of 
precipitation occurred. The amount of precipitate gradually increased when the 
concentration of the zinc salt rose from 0:001 to 0°05 normal. As the concentration 
increased beyond this point, the amount of precipitate formed gradually diminished until 
a concentration corresponding to that of a normal solution was attained. At this point 
