Vol. 1, No. 1
ANALYTICAL EDITION
56
S u m m a r y of Tests Using Goodrich R u b b e r a n d Rubber-Sulfur Formula TTraann- ..--..-
Maxima a n d M i n i m a (Five laboratories; seven tests; Firestone formula) MAXIMA MINIMA
FIRESTONE SIMPLEX
6.6. -. ~.. r N u T ECURE
Tensile a t 700 per cent elongation Tensile a t break Per cent stretch a t break
124 229 850
72.3 174 775
169 238 823
108 197 737
191 265 781
135 204 696
Tensile a t 500 per cent elongation Tensile a t 800 per cent elongation Tensile a t break Per cent stretch a t break
90-MINUTE CURE
a
Tensile a t 700 per cent elongation 218 Tensile a t break 269 Per cent stretch a t break 784 Thcrmatomic Test No. 1, 75-minute cure omitted.
141" C. 2 6 . 4 ' C.
15.6 54.5 128 947
12.7 52.3 142 963
14.5 61.2 141 958
20 70 142 915
16.9 76 181 927
22.9 81 131 878
18.4 89.4 163 895
180-MINUTE CURE
%-MINUTE CUREa
Tensile a t 700 per cent elongation Tensile a t break Per cent stretch a t break
ATOMIC
141° C. 2 2 . 2 ' C.
ISC-MINUTE CURE
Tensile a t 500 per cent elongation Tensile a t 800 per cent elongation Tensile a t break Per cent stretch a t break
BO-MINUTE CURE
Tensile a t 700 per cent elongation Tensile a t break Per cent stretch a t break
141' C. 26.1'C.
Curing temperature Testing temperature
16.9 71.8 135 906
210-MINUTE CURE
152 214 703
Tensile a t 500 per cent elongation Tensile a t 800 per cent elongation Tensile a t break Per cent stretch a t break
18.6 83 161 894
S u m m a r y of T e s t s Using Goodrich R u b b e r a n d Firestone F o r m u l a (Curinp temperature, 137.4-137.7O C.) . -~
GOOD- SIM- SIM-
PIRESTONE THERMATOMIC I Run I1 Run I Run I1
MONS Run
RICH
PLEX
Tensile'" a t 700 per cent elongation Tensilea a t break Per cent stretch a t break
119 215 798
112 206 791
108 213 803
Tensile a t 700 per cent elongation Tensile a t break Per cent stretch a t break
155 233 783
151 229 775
141 238 790
Tensile a t 700 per cent elongation Tensile a t break Per cent stretch at break
191 248 753
183 244 753
166 265 781
REMARKS
ICMINUTE CURE
80
174 838
123 192 775
72.5 189 880
100 229 830
Goodrich testing temperature 23.3
Simplex testing temperature 22.2O C.
108 238 823
122 223 806
Thermatomic, Run I, testing temperature 26.7' C.
75bt~ 226b 807b
171 255 756
Thermatomic, Run 11, testing temperature 26.1' C.
187 267 760
Thermatomic, Run 11, tested June 22, 1928
C.
BO-MINUTE CURE
112 197 790
169 209 737
Simmons testing temperature 23.3' C.
?&MINUTE CURE
135 204 768
202 214 696
Thermatomic, Run I, tested March 29, 1928
SC-MINUTE CURE
209 190 218 Tensile a t 700 per cent elongation 269 253 242 Tensile a t break 723 755 727 Per cent stretch a t break a "ensiles are expressed in kilograms per square centimeter. b Obviously wrong, because it is inconsistent with other cures on c Error in transcribing. Correct figure is 117.
162 213 740
213 217 703
152 264 784
same stock.
Specifications for Standard Gelatin' Report of Committee on Standard Gelatin Appointed by Division of Leather and Gelatin Chemistry
A
T THE Detroit meeting of the AMERICANCHEMICAL SoCIETY a t the suggestion of S. E. Sheppard, a committee
was appointed by this Division to study the problem of making a standard gelatin. During the course of the year the three members of this committee, have exchanged copious correspondence on the subject of gelatin. It is apparent that more than one standard for gelatin is necessary inasmuch as we have different kinds of gelatin such as pigskin, calfskin, ossein, bone, etc., and inasmuch as the previous history of gelatin affects its character, and inasmuch as some gelatins are cooked on the acid side of the isoelectric point while others are cooked on the alkaline side. To simplify the chaotic situation it seems advisable to start with one standard gelatin, preferably one which may be used from the scientific rather than from the commercial standpoint. Accordingly, we submit the following tentative specifications for standard gelatin for physico-chemical purposes: 1-The gelatin should be calfskin gelatin made from green stock, limed for 3 months, scoured, washed, and extracted at 130' F. (54.4' C.), only the first run being used. The gelatin should be dried a t not less than 5 per cent concentration, which may require vacuum evaporation of the stock. 2-The gelatin should be de-ashed t o an ash content of not greater than 0.05 per cent. &The gelatin should have a constant isoelectric point. &Under standardized conditions and a t a definite given concentration it should have a definite viscosity. Just what this viscosity is is not of primary importance. &Under standardized conditions and a t a definite given concentration it should have a definite jelly strength. Just what this jelly strength is is not of primary importance. 6-The gelatin must be clear-that is, have a minimum turbidity in a 5 per cent jelly. 1 Received
September 20, 1928.
7-The gelatin must be free from color-that is, have a minimum absorption of blue light at a definite thickness of a 5 per cent jelly. 8-The gelatin should have a certain minimum content of fat or grease, which amount is t o be determined (probably less than 0.1 per cent). 9-The gelatin should contain not more than a certain minimum-say 0.1 t o 0.2 per cent-of heat coagulable protein. 10-Inasmuch as we are using isoelectric gelatin, preservatives should be absent. Additional specifications may be added as they suggest themselves, but the committee feels that those enumerated above are sufficient to start work. It might be advisable t o have a standard gelatin for biochemical and bacteriological purposes. We believe that the specifications enumerated for standard gelatin for physico-chemical purposes could apply to a standard gelatin for biochemical and bacteriological purposes with some additions.
As regards heavy metals, it shall not contain arsenic in excess of 0.5 p. p. m. as Asz03. It shall not contain zinc in excess of 20 p. p. m. It shall not contain copper in excess of 10 p. p. m. It shall not contain other heavy metals in excess of 50 p. p, m. The methods of determining these metals shall be those prescribed by the A. 0. A. C. We believe that samples of this standard gelatin should be submitted to various workers in the field to determine the physicochemical constants thereon. Secondly, we believe that subsequently other standards should be devised t o take into account the different kinds of gelatin and the different methods of preparation. CLARKEE. DAVIS S. E. SHEPPARD M. BRIEFER
