I
.
'I'hc desiccator herein described was primarily designed by the writer for use in rubber analysis but it might advantageously be used for other lines of organic work. I t is simple in construction and inexpensive. -4s is well known, the amount of moisture in the various rubbers is a n important factor in the manufacture of rubber goods as its presence is apt to cause trouble. In the determination of moisture in rubber, the removal of the last traces of moisture is very difficult on account of its being adsorbed by the rubber colloid and very tenaciously held. For quick moisture
t o the nature of the rubber and amount of moisturc: i t contains. I t was for the purpose of more rapidly making this determination of moisture and for drying the rubber a t various stages of its analysis that this desiccator mas designed. The following sketch illustra.tes its construction : Fig. I shows the details of the apparatus. I t consists of a n ordinary vacuum desiccator, '4, containing Ltri electric heating coil, C . The coil C is made from ztri ordinary I/,-inch porcelain insulator tube six inches long and fitted with a square piece of fiber a t each end as shown. The tube is wound with twelve feet of No. 34 nichrome wire, the latter being secured to two terminals a t either end of the coil. Two insulated wires, connected t o the terminals of the coil, pass out
t c s t s which need be only approximatc, such as for factory control the rubber can be dried in air a t 100' C. to approximately constant weight, but this method invariably leads to oxidation of the rubber by the a t mospheric oxygen. 'This latter can be avoided by drying the rubber in a stream of illuminating gas a t T O O O C. but again a serious error results, due t o the absorption by the rubber of certain constituents of the gas. The usual method is to place the finely divided rubber on a watch glass in a desiccator and dry over sulfuric acid or calcium chloride i ? z vacuo. This method, however, while giving good results, requires from twenty-four hours to a week, according
of the desiccator through the rubber stopper at S ant1 are connected by flexible lamp cord t o a lamp rheostxt .coiisisting of four 16 c. p. incandescent lamps coniicctc~ti in series parallel. The tube B,communicating wit11 the interior of the desiccator, is connected by rubbc,r tubing to a manometer and vacuum pump. The tray D , for supporting watch glasses, etc., is made of shect metal to aid in radiation of heat and is shown in detail in Fig. 2 . The temperature of the desiccator is controlled by the lamp rheostat. 13y turning on one or more lamps either in series or parallel, a range of temperature. varying from 4j0 C. t o 1 7 5 ' C. can be obtained. A thermometer, T , indicates the tempera-
AN ELECTRIC DESICCATOR FOR THE ANALYSIS OF INDIA RUBBER AND OTHER ORGANIC COMPOUNDS B y L. J. D. HEALY Received April 1 , 1913
CHEMISTRY T H E J O liRN-4I, O F I-VD li.STR1A L d.VD E~VIGILVEEKI~VG
490
ture within the desiccator. The lower part of the desiccator is p a r t l y ’ filled with anhydrous calcium chloride. The procedure is as follows: The finely divided rubber is weighed on a watch glass and placed in the desiccator. The air is exhausted and the electric current turned on. Usually one lamp is sufficient and will maintain a uniform temperature of about 60’ C. If necessary the temperature may be further reduced by placing two lamps in series. The electric current is left on for one hour and, if during t h a t time the vapor pressure within the desiccator becomes greater than 7 5 mm., the stopcock a t S is opened and the vapor exhausted. At the end of one hour the electric current is turned off and the desiccator allowed to cool. Air is then slowly admitted and the desiccator is again allowed t o stand for some time until the last traces of moisture have been absorbed by the chloride. The rubber is then weighed and the procedure repeated until the weight of the rubber is constant. For control purposes, one heating is usually sufficient. Very satisfactory results have been obtained with this type of desiccator in the analysis of rubber and compounding ingredients used in the manufacture of rubber goods. The removal of the air prevents oxidation and the heat produced by the coil, while not enough t o injure the rubber, is sufficient t o rapidly vaporize the water a t the prevailing pressure within the desiccator. For soft rubbers a thin sheet’ of dried asbestos may be placed on the tray D , to reduce the radiation of the heat from the coil. The following tables offer a fair comparison between the ordinary type of vacuum desiccator and the electrically heated desiccator and give some idea of the time saved. TABLEI-MOISTURE DETERMINATION ON GUAYULE Elcctric vacuuui de4ccatm Ordiunry vacuum desiccator Per ccnt Per cetit No lioiirs moisturc No.hours inoisture 40 . . . . . . . . . . . . . 2 3 . 6 I . , . . . . . . . . . . . . . . . . . . 20.2 (,‘I . . . . . . . . . . . . . . . . 88 . . . . . . . . . . . . . . . . . . . 136 . . . . . . . . . . . . . . . . . . . lhO., . . . . . . . . . . . . . . . . . . .
28.5 30.1 32.2
1x4 . . . . . . . . . . . . . . . . . . .
33.1 33.3
208 . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . 31.3 . . . . . . . . . . . . . . . 33 0 4’/a.. . . . . . . . . . . . . . . . . . 3 3 . 5 2’/2.. 31/2,.
32.x
TABLE11-CONGO KUBBEX Ordinary vacuum desiccator Electric desiccator Per cent Per cent Nu. hours moisture N o . hours moisture 24 . . . . . . . . . 4x.. . . . . . . . . 72.. . . . . . .
.........
0.84
. . . . . 1.02 . . . . . . . 1.02
2.................... 3 ....................
0.9x 0.38
As shown in Table I, one portion of a sample of crude guayule approached constant weight after z o S hours when dried in an ordinary desiccator, against 4 1 / ~hours for a portion of the same sample dried in the electric desiccator. Again, Table I1 shows that a sample of Congo required 7 2 hours for check weight against 3 hours when dried in the electric desiccator. 152 MAPLE ST. NEW
BRITAIN, CONN.
V O ~5. , NO. 6
A COMPACT, ACCURATE BURETTE FOR USE IN NITROGEN WORK OR WHENEVER MANY MEASUREMENTS OF STANDARD ARE NECESSARY B y FRAKKC. GEPHART
Received April 8. 1913
The accompanying drawing illustrates a burette devised for use, primarily, in Kjeldahl work but applicable in all lines of work where i t is necessary to make repeated measurements of standard solutions. The burette consists of three bulbs, blown without shoulders and delivering z j , I j , and I O cc., respectively. Two portions of 2 5 cc. each may be drawn without refilling, or likewise I O , 1 5 , 40 or 5 0 cc. From the top meniscus mark t o the lower measures 6 1 / 2inches, thereby placing each meniscus in easy reading distance without rising to adjust the zero. The stopcocks are provided with borings a t the end through which is driven a small piece of wood in front of which has been placed a small rubber washer, thereby rendering “lifting” impossible. This burette may be secured from Eimer & Amend, New York City. ’
RUSSELL SAGE INSTITUTE OF PATHOLOGY NEWY O R K
A COMBINATION APPARATUS STAND E. R . SQUIBB& SONS Received April 1 5 , 1913
I3y
’I’his dcvice has been in use in the research laboratory of E. R Squibb & Sons for some time and has proven very satisfactory in practice. The apparatus consists of a nickel-plated, upright rod, about 2 2 inches in height and I / ~ inch in diameter, secure(1 in a n iron cylinder base weighted with lead. Several attachments, adapted for various chemical manipulations, can be fitted t o thc rod. These proposed attachments consist of (see drawing) spring clamps which slide closely over the rod and lock automatically - by - binding o n the same. A clamp is easily shifted up or down or swung sideways by a slight pressure. The advantage over other such stands is its stability, neat appearance and compactness. The stand is simple, portable and can be used for many simultaneous operations. I t s uses are: I . For filtering (can hold four or more funnels). 2 . For holding burettes absolutely rigid, and perpendicular, permitting them to be easily moved up or down. Each stand may hold 2 or more burettes
n
