Laboratory Apparatus for:
THERMOLYNE SYBRON CORPORATION
(9^HEAT LIGHT
MOTION
Report for Analytical Chemists
repeated analyses is
/we
can
apply Equation 15 to the average as a new variable and write it in the following way, with e as an arbitrary small number: V{\xM
X\>
-
(16)
e)
It should be noted first, that deon the measuring procedure, while e can be chosen according to our intent. Therefore, the probability that the average of a series will not deviate more than prescribed from the mean X (often considered as the true value) can be made as small as one likes by making the number M of repeated measurements sufficiently high. This is the “Law of Large Numbers” and it is the basis for the “representative method” of statistics. It justifies our expectation that a longer series of observations (M large) in general—but not necessarily—will give better estimates for the mean, the standard deviation, and the probability function of the parent population than a short one. For the practical application of Equation 16, we should know the value of . It may be too daring to take the standard deviation, s, of a short series as an estimate, but from previous observations we may know an upper bound for ; any finite but constant number will do. For example, there may be experimental restrictions for the range of the variable x between Ziow and Xi.jgh. Then certainly is < (¿‘high aw)· Replacing in Equation 16 by such an upper bound makes the inequality weaker, but not ineffective. To demonstrate the application of Equation 16 to an experimental decision, let us suppose that we know pends only
(THEHMOLYHE) 600
Off
hot plate with ceramic sealed heaters Nucerite combination ceramic-metal composite. The glass hard ceramic surface of Nucerite does not corrode, discolor or distort. At the very top temperatures, color, surface smoothness, imperviousness, and construction remain unchanged. Nucerite keeps its integrity in every respect.
HIGH HEAT TRANSFER EFFICIENCY All external surfaces of the Nucerite top are ceramic. The heating element, a printed circuit type, covers the underside of the disc and is fused between layers of ceramic. The element is hermetically sealed by a thin, but highly effective electrical insulation.
CORROSION RESISTANT SURFACE The ceramic component of Nucerite offers the inertness and corrosion resistance common to borosilicate laboratory glass. Nucerite is unaffected by most acids and alkalies.
TRY NUCERITE ON THESE TYPICAL LAB USES Preparing culture media, heating
NEW NUCERITE TOP PLATE
is
—
a
—
FAST HEAT-UP AND RESPONSE TO CONTROL Temperature rises to a maximum of 600°F from ambient in 3-4 minutes. The low mass, fine conduction of Nucerite
—
—
chemical
resinous solutions, warming material, melting paraffin, semi-conductor fabrication, heating reagents, evaporation and distillation tests, soil analysis.
—
top and the demand thermostat impart usual control: +3°F.
un-
RESISTANCE TO ABRASION—The smooth glassy surface of the Nucerite top will not deteriorate from abrasive wear under normal conditions. The hardness rating for Nucerite on the Moh's Scale is 6-7. FLAT NON-STICK SURFACE cleaned and will not discolor.
N
E XA^
CAT
—
L
is
easily
LOW SILHOUETTE DESIGN Only 3 inches high, the hot plate is stable, takes less lab space and is eye-pleasing. Vinyl covered steel case and Nucerite top are finished in restful soft two-tone green. Dial surface is recessed to forestall discoloration and chemical attack. Nucerite Hot Plate is 7 x 7 x 3 inches high with top plate diameter of 6% inches. Furnished with pilot light, 3-prong grounded cord and plug. 120 Volts, 50/60 Cycles, 950 Max. Watts. Model HP-11415B -
—
$40.50.
TABLE III. PROBABILITIES OF DEVIATIONS
^3 48-Page catalog shows expanded lines: furnaces, controls, hot-plates, magnetic stirrers, Stir-Plates, Stir-Lights, Dri-Baths, incubators, lab-lights, meters. —
\x Factor k
Write
today for your
FREE
copy
A THERMOLYNE
42 A
4 5
X\>
For any
distribution,
p smaller than
k
For “normal” distribution, p equal to
1/4 1/9 1/16 1/25
(nearly) 1/22 1/370 1/16000 1/300000
1/100
~0
SYBRON CORPORATION
2555 Kerper Blvd.
Dubuque, Iowa 52001
Circle No. 68 on Readers’ Service Card ·
2 3
-
ANALYTICAL CHEMISTRY, VOL. 42, NO. 4, APRIL 1970
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