deletions | additions       diff --git a/A_bottle_of_the_substance__.tex b/A_bottle_of_the_substance__.tex  index bd86e37..2c1a192 100644  --- a/A_bottle_of_the_substance__.tex  +++ b/A_bottle_of_the_substance__.tex 
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A bottle of the substance on which NMR was being performed could be inserted into the center of the solenoid (Fig. \ref{fig:coils}). In this experiment, $H_{2}O$ was used. The parts of the apparatus which were key to performing the NMR are the solenoid, Helmholtz coils, and gradient coils. \\\\ %All of these could be varied separately, as could the bandpass filter; they are discussed below.  The A  solenoid with a coil constant of 15mT/A was used to apply a magnetic field to polarize the water. The magnetic field of the solenoid, which was the polarizing field, could be varied using a variable current input. The field of the Helmholtz coils, which artificially increased or decreased the Earth's magnetic field applied to the sample, was adjusted using a separate variable current input. The gradient coils could have changed can be used to change  the gradient of the magnetic field in the x, y, and z directions. In our experiment, the gradient coils were used to create a homogeneous field. field but were otherwise not adjusted over the course of the experiment.  \\\\ A bandpass amplifier, part of the NMR instrument, was tuned to resonate at the Larmor precession frequency. The bandpass amplifier restricted the frequencies to those around the Larmor precession frequency, and reduced any background noise such as 60 Hz fluctuations in the field due to fluorescent lighting in the room, as well as amplify the precession frequency. \\\\