Dec., 1920
T H E J O L'RNAL O F I N D C S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
CAUTIONS TO B E O B S E R V E D I N THE PERFORMANCE OF THE TEST
I-Casein of low salt content is wetted with water slowly; hence when adding the 0. 2 M borax solution t o the casein i t must be done with rapid stirring; otherwise lumps will form which dissolve at a slow rate. High fat content casein also wets slowly. 2-High solution temperature (above 35' C.) must be avoided, else the results become uninterpretable from the standpoint of the physical nature of both the casein and the solvent. 3-Casein which contains much fat behaves differently from others. It acts much like high temperature casein during the early stages of the test; viz., i t dissolves slowly and tends t o form a gel simulating dilute gelatin or agar. If i t is not a heated casein i t begins t o disperse after 15 or 2 0 min., with frequent stirring, and a t the end of 30 min. i t may be entirely dissolved, b u t the solution will be very milky and its consistence less cohesive or less mucilaginous than that of a casein without much fat. If i t is a hightemperature casein containing much fat, the solution is irregular, milky, and gelatinous a t the end of 3 0 min. The following tabulation (Table 11) shows the rela4 v e consistence and some physical appearances of caseins when treated as in the revised test. TABLE11 PHYSICAL CONSISTENCE OF SOLUTIONS IN 0 . 2 M BORAX After 30 min. After 15 min. Stiff gel; Stiff gel. Commercial sulfuric' Some unhissolved; undissolved; temperature 1200 k.; clear clear ash 5.04 per cent Mostly dissolved; In solution; :Natural sour; low temp.; smooth. smooth: ash 3.69 per cent mucila&nous1 mucilaginous :Kahlbaum casein "nach Dissolved. Dissolved: smooth and clear: Hammarsten;" low temp. smooth add clear; mucilaginous mucilaginous Stiff gel; Stiff gel; Cooked curd sulfuric; undissolved ; undissolved; temp. 128' F.; clear clear ash 5.58 per cent Modified cooked curd. Gelatinous; Still very gelatinous; some undissolved; hydrochloric much dissolved; temp. 120°F.; acid; ash 4 . 8 2 per cent cohesive cohesive Dissolved; clear; Dissolved; clear and Grain curd: hydrochloric; smooth solution; smooth; temp. 95O F.; mucilaginous mucilaginous ash 2.55 per cent Natural sour; high fat. Gelatinous; Mostly dissolved; milky; fat 9.5 per cent; no &story undissolved; of temperature milky white cohesiveness poor Stiff gel; Gelatinous. Buttermilk. natural sour; undissolved; mostly dissblved; temp. 12bo F.; somewhat milky cohesiveness poor fat 4 per cent Neutralized cream butterGelatinized in chunks; Mucilaginous; milk casein; temp. 150' F. undissolved; mostly dissolved, for 50 min.; precipitated translucent translucent. at 125" F.; purified to an ash of 1 . 0 7 per cent 1 Mucilaginous is used in the sense of describing a very sticky fluid, and connotes cohesiveness.
TYPEOF CASEINAND 'METHOD O F MANUFACTURE
The chief value of the borax test is t o determine whether the casein under examination exhibits suitable working properties, when dissolved b y certain alkalies. It should be borne in mind t h a t i t is not designed t o give direct evidence of the actual value of a casein for glue making, paper sizing, paint preparation, or any other industrial product. Only direct and unprejudiced trial will determine the actual value. But the method as revised does serve t o classify differentially the caseins according t o certain inherent properties, depending upon the source and method of separation. It very rigidly differentiates
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between high- and low-temperature caseins. The cooked-curd caseins without fail tend t o imbibe water and form a jerly in this test. They are also unsuitable for certain industrial operations, but are valuable for others. The test also serves to give evidence of the presence of fat in casein. It readily isolates those caseins which dissolve quickly t o give solutions of even fluidity and translucence. While the principle of this test is founded in viscosity phenomena, the use of a viscosimeter is avoided by choosing concentrations and conditions which yield viscosity data of interpretable value b y a simple test. I t was a matter of great satisfaction t o find t h a t the casein produced by the grain-curd process without heat treatment, and with the idea .of isolating casein by the most direct method, yields uniform and promising solutions with the improved borax solubility test. SUMMARY
I-The viscosity curve of casein in borax solutions shows t h a t the maximum viscosity is obtained at a H+-ion concentration of p H 8.15, while a t a p H of 8 . g t o 9 . I the viscosity is less but constant, owing t o the buffer effect "of borax in this region. The importance of conducting the borax test in this buffeted region is discussed. 2-The great variation in the t.iscosity of casein solutions a t different concentrations of casein is utilized in the improved test by choosing a concentration which will bring o u t the difference in physical constitution of casein prepared under safe and dangerous temperature conditions. 3-The viscosities of several caseins in borax solutions are given to show that differences in the physical structure of caseins have greater influence upon their viscosity than the normal contaminating substances present in commercial caseins. High-temperature caseins always exhibit a comparatively great initial viscosity. 4-The essential changes in the improved caseinborax test include low solution temperatures, reduced concentration of casein, and increased concentration of borax. These changes are based upon purely physicochemical relationships. 5-The value of the casein-borax test is defined as an accurate means of differentiating between lowand high-temperature caseins.
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CELLULOSEACETATES By J. 0. Zdanowich JAMES ST.,LONDON, s. w. 1 , ENGLAND Received August 12, 1920
During the war, when cellulose acetate was found the most suitable material for aeroplane "dope," complaint was often made of the quantity and also the quality of the material a t hand. With the active encouragement of the British Air Inventions Committee the writer has developed a new process1 for the manufacture of cellulose acetates, which is even more suc1
U. S. Patent 1,347,801 (July 1920).
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