in Figure 3 is characteristic of the bndycentered cubic lattice of frrrite (latticc constant, 2.86 A,). The edge of the specimen in Figure 4 was sharpcncd by elt.ctrical polishing in order to remove the transformrrl ferritic layer. The series of diffraction rings from the specimen in Figure 4 arc characteristic of the face-centered cubic lattice of the austenitic substrate (lattice constant, 3.52 A,). According to these interference experiments, the content of the ferromagnetic ferritic inclusion in Figure 3 is larger than that of Figure 4. This interference method corrcsponds to a crossexamination in the magnetic analysis of the stainless steel. A chemical analysis of the ferromagnetic inclusion found in the specimens was not carried out in the prenent study. The crystallographic analysis by a diffraction experiment plays not only the part of a chemical analysis, but it also supplements the magnetic analysis. Measurement of the eccentricity of the diffraction rings madc it possible to pstimate the magnetization of the test pircc. The following relation exists between the deflection of the electron beam (Az) and the magnetization, B, under the prrsent conditions.
This Q value is measurable in the present process. The same size test piece n-as employed-i.e., the thickness of the specimen (lo) was always kept constant. The ferromagnetic particles included in the tcst piece were magnetically oriented by the process of mechanical polishing. According to Equation 2 the 6? value was measured as the average magnetization of the specimen, and it is approximately proportional to the amount of the ferromagnetic inclusions formed in the specimen. In Figures 3 and 4, Az
=
0.4 1 mm. (A = 0.0294 A.)
and A= = 0.1'9 mm.
Figure 4. Gold and stoinless SI 'eel. The specimen was polished electrim3lly; weak Lorentz effect observed
(A = 0.0304 A . )
was measurecI, respectively. According to Equation 2,
WT~VP length, 0.0304 A
Q
=
1.2:i gauss cm. far Figure 3
Q
=
0.52 gauss cm. for Figure 4
and where e is electron charge (1.6 X lo-" emu), L is the camera length (495 mni.), k is the wave length of the incident electrons, h is Planck's constant (6.6 X lo-" erg. see.), and Io is the thickness of the specimen. From Equation I we obtain
were obtained. Thus the process of electron diiTraction makes it possible to study the ferromagnrtic inclusions formed in stainless strcl. It would be of interest to estimate the resistance of austenitic stainless steel (18-8) in the strain-induced transformation.
Collection Unit for Gas-liquid Chromatography under Reduced Pressure 6. M. Craig, T. M. Mallard, and L. 1. Hoffman, Prairie Regional Loboratory, National Research Council. Saskatoon, Saskatchewan, Canada HE METHYL ESTERS
of CL2to C2*
T fatty acids have been separated on a gas-liquid chromatographic apparatus.
The initial work in this laboratory was done on a unit operated at reduced pressure. Difficulty was experienced when an attempt was made to collect the individual fractions. Some condensation in the exit tube was encountered and in addition pressure disturbances introduced by changing receivers distorted the recorded signal from the detector cell so that the area under a given peak could not he used to estimate the weight of the fraction with sufficient accuracy. The collection unit is equally suitable for chromatographic units operated a t atmospheric pressure. The simple collection unit devised to overcome these problems is illustrated in Figure 1. A stainless steel tube with a 3-mm. bore and a tapered female joint formed the exit from the detector cell. A stainless steel section with a tapered male joint at one end and a tapered female joint at the other end
joined by a 3-mm. hole was marhined from a cylindrical block. Two holes were drilled at opposite sides of the hlock into the female tapered section and were fitted with No, 15 hypodermic needles with the needle points outward. A Teflon stopcock was machined with a groove along one side to allow vapor and gas passage to one needle a t a time. A cylinder was soldered around each needle exit to providc protection from cooling. The entire block was mound with heatcr wire which was connerted to a 110-volt source through a Variac transformer. The block !vas placed in a metal container par,ked uith glass u-001 for insulation. The hlock and hypodermic needles were maintained a t n temperature IO' to 50' C . above the operating temperature for thc column, preventing condcnsation of any material within the apparatus and eliminating any possibility of contamination of samples. The Teflon stopcock did not show deterioration after 6 mouths' continuous use. The collectors were made of 8-mm.
Pyrex 7i4 glass tuhing as illustrated. Small glass beads were placed in the U-tube to provide surface for condensation. The U-tubes could be placed in dry ice baths to minimize losses by evaporation. The enlarged end of the U-tube \vas sealed rrith a silicone ruhber disk, which had a small hole to permit entry of the hypodermic needle. A frontal vicrv of the assembly is also shown in Figure 1. .icommon line of '/
