‘334
J . H. LONG
compounds may be deduced by considering the ease with which alcohols form addition-prodncts with other nietallic chlorides good exaiiiples of which for instauce, are SnCl,.zC,HjOH aiid SiiC1,. zC,H,,OH. T\’he11 we treated stannic chloride with an excess of propyl alcohol we obtaiued no propyl chloride b u t a liquid boiling at I@’. Elid-products of the PCl,--ROH combinations have already been mentioned ; their intermediate products, theoretically considered, may be many ; these intermediate products may give directly by heating or under the influence of zinc chloride and heat, the required alkyl chloride. h study of these iiiterniediate products will be made. r K I I I S A . ILL.
~-
ON THE COMBINING POWER OF CASEIN WITH CERTAIN ACIDS. By J . l i . LON(:.
Received J u l y
11.
i90j.
In several recent papers I have shown the amount of different alkalies which may be combined with a given weight of casein to form salts,’ and have also pointed out t h e behavior of hydrochloric acid i n conibiniiig with tlie products of casein hydrolysis brought about by prolonged digestion in presence of pepsin, with subsequent heating.’ These results suggested another liiie of enquiry, ziiz : --the combining behavior of t h e acid, without the aid of pepsin, at tlie ordinary temperature as well as a t higher temperatures. T h e amount of acid combinitig at the ordinary temperatures may in many cases be found by simple titration, while for higher temperatures other means may be employed. At the ordinary teinperatures inaiiy dilute :icids combine with casein as with other proteins to form salts, and the amount of acid so held is definite and constant. By n a r n i i t ~ g hoivever, , or by prolonged contact, t h e acid5 lead to the formation of hydrolysis products, some of which as amino acids, are strong enough to hold considerable quantities of the acids used as the conibiniiig and hydrolyzing agents. It was shown in the last papers quoted that the aniount of hydrochloric acid held in this way is about what might be espected from the character of the aniino acid groups probably developed. But it1 the present inqniry we are concerned with the activity of the acids wheu not assisted .by the digesting power of the pepsin, and the first experiiiients were made with N/ro hydrochloric acid a t tlie ordinary temperature, followed by sotiie in which the combination was effected by heat. Hyd~ochloricAcid. --A series of tests was made, using always 5 grams of pure caseiu prepared by the Haniiiiarsten process and varying aniounts of t h e weak acid, with water enough to make up always I O O cubic centimeters. T h e mixtures of weak acid and casein were allowed to stand This Journal, 27, 3 6 3 ; 2 8 , 3 7 2 . Ibitl. 2 9 , 2 2 3 ; 29, 29j.
I335
COMBINING POWER OF CASEIN
ibout an hour with frequent shaking, and were then filtered, which, u p With stronger icid mixtures, however, a jelly-like mass was formed which could not be iltered rapidly or perfectly enough for the purpose. When a filtrate could be secured, it was used for titrations with limethylaminoazo benzene, phenol-phthalein and p-nitro-phenol, in most :ases. Conductivity tests were frequently made on a part of the filtrate. In the mixtures which became too thick for filtration the whole was used for the titrations directly. T h e results obtained are shown in the following table, where the result of titrations with 2 5 cc. are reduced t o I O O cc. for comparison : :o a certain strength of the acid, was readily possible.
TABLE CC. N / I O HC1
CC. Water
cc.
~.--j
GM. CASEIN 4- HCI.
cc.
Xi10 N a O H . Orange
X/ro R’8OH. Phenol-phth
2.8 4.9
5
95
0.0
IO 15 20
90
0.0 0.0
12.0
..
0.0
16.0
25
75 70
0.0 0.0
25.0
65 60
trace 4-
..
30 35
40
85 80
...
. . .. 30.0 35.0
40.0
cc.
Conductivity
N’IO X a O H .
p-Xitro-phenol
K:O
2.4
0.000275
.... ....
4.0
0.00044j
....
0.000946
25.0 30.0 35.0
Jelly, titrated whole mixture
0.000i39 ,
. . . .. ..
