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Archive for the ‘Science’ Category

Crystal Growing

Posted by aonomus on April 5, 2010

So a simple and try-at-home type of experiment is to take colourful water soluble transition metal salts and try crystal growing. The results are usually either extremely frustrating (a mush of wet crystals) or rewarding (a nicely formed crystal). Crystallization is a process used to purify compounds by rejecting dissimilar compounds from joining the crystal structure, as well as to grow crystals of proteins to determine their 3D shape via other analytical methods; most importantly its a practice in patience.

The trick to crystal growing is to saturate the solution and slowly evaporate solvent (water), eventually a imperfection in the container surface or simply enough of the compound aggregates and a crystal structure starts to form. If the solution is saturated and the solvent removal continues, more of the salt will crystallize onto the existing structure, yielding a single crystal. However removing solvent too quickly can yield a large lump of varied crystals.

Here are some crystals I’ve grown before: from left to right: CuSO4, FeCl2, and CoCl2. The 3rd vial containing Ru3(CO)12 is just another colourful sample I had on the shelf.

A closer shot of the CoCl2, its particularly hard to grow a crystal where the level of chloride can determine CoCl2/CoCl42- equilibrium. I may try recrystallizing this after fully dehydrating this under heat to drive off all excess chloride (this CoCl2 was made from CoCO3 + HCl, thus excess chloride may have been present). Note how dark the crystals are, my camera won’t even pick up the colour – they are actually a deep purple with some thin crystals present that you can actually observe the colour.

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DIY Syringe Pump Version 3!

Posted by aonomus on April 2, 2010

So after a completely failed iteration of the syringe pump (constant jamming of the syringe plunger, hair pulling, etc) that followed the first pump, I’ve come up with a much more compact syringe pump that fits onto a standard project case.

The main difference between this version, and the previous version is the orientation of the mechanisms. The original had the stepper motor behind the plunger, while this version has ‘folded’ in on itself, and has the stepper motor underneath the syringe. The effect is a compact syringe pump that does not take up the entire desk.

The next step is to bolt the pump assembly down onto the case, design the software for a PIC based controller for standalone operation with optional external control, and actually use this for microfluidic devices.

Posted in Chemistry, Electronics, Projects, Science | Tagged: | 4 Comments »

Ferrous chloride synthesis procedure

Posted by aonomus on March 6, 2010

Introduction

This document outlines the synthesis of the air sensitive compound ferrous chloride tetrahydrate using non air-free technique. Ferrous chloride can be used as a source for iron(II), as a oxygen scavenger, reducing agent, and precursor to magnetite.
Read the rest of this entry »

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Crystal growing and air sensitive compounds

Posted by aonomus on February 27, 2010

In preparation for making my own ferrofluid from scratch, I made a large batch of FeCl2 by reducing FeCl3. The only catch is that its air sensitive even in solution, trying to boil it down or dry it out in air will result in oxidation to a mixture of oxides and hydroxides. After making the FeCl2 solution, vacuum distillation was used to dry out the mixture, followed by cooling, and recovery.

A parallel experiment was run using FeSO4 -> FeCO3 -> FeCl2 in solution, which was dried using a desiccator over 2 months. After only partially drying, the liquid was removed, crystals washed from FeCl3 impurities, and finally put in a desiccator to dry.

So finally, some eye candy.

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Extraction of capsaicin from Scotch Bonnet peppers and determination of the Scoville Rating

Posted by aonomus on February 17, 2010

So a soxhlet extractor has been on my list of  ‘cool glassware to get’ (right next to an actual fractionation column out of glass, with real plates). I suppose the first experiment I can try is to extract capsaicin from habanero peppers, and then get a panel of friends to try serial dilutions of the extract to determine its Scoville heat rating.

Preface and Warnings

  • Pure capsaicin powder in milligram amounts can cause severe skin blistering, burns, and reported nerve damage
  • Oleoresin (the desired target of this procedure) can also cause severe skin blistering and burns.
  • Use full personal protection equipment (lab coat, goggles, gloves) and have an eye wash ready
  • Use a dust mask (preferrably N95) when handling dried peppers

Procedure

Pepper preparation

  1. Start with 10 unripe Scotch Bonnet peppers, they should be firm, not leathery or soft.
  2. Cut peppers into quarters, separate out seeds manually (contains the largest amount of capsaicin), place into pyrex containers, chop peppers finely*. Place into an oven, and begin drying at minimum setting (preferrably under 100degC). *Ideally, a blender can be used once seeds have been separated.
  3. Remove seeds when dry, allow peppers to dry fully, stir as needed
  4. When fully dry, begin next procedure segment.

Soxhlet extraction

  1. Set up 250mL round bottom flask in heating mantle or water bath, add clean, new boiling chips, and 100mL 95% ethanol.
  2. Place soxhlet extractor onto flask, fluff 1 or 2 cotton balls and place at the bottom of the extractor (pack with a glass rod).
  3. Add dried seeds to extractor, and level out. Add pepper flesh until full* and level out. Place another 1-2 cotton balls ontop and pack gently with a glass stir rod.
  4. Fit adapter (depends on extractor construction) and condenser to the extractor. Begin heating to boiling.
  5. Maintain heating and replenishing water bath as necessary for 2 hours (typically until ethanol coming off the extractor is clear).
  6. Proceed to concentration step.

Note: at this stage, assuming a ideal sphere of 2cm radius with 10 peppers gives a volume of 335mL reduced to 100mL ethanolic solution. You can try to taste test this carefully, pipette off a small aliquot (approx 0.2mL) to a clean Eppendorf microtube, and use a clean qtip or coffee stirrer to sample a small portion and touch it to your tongue. You may notice that the spicyness is not very strong, however once fully concentrated, the extract will be hazardous to sample in this method. Do not try this with any higher concentrations of capsaicin extract.

Concentration

  1. If available, use a rotary evaporator with a bump-trap to remove solvent.
  2. Set up a distillation apparatus, evaporate solvent under reduced pressure carefully to prevent bumping
  3. Allow concentrate to stand overnight in a sealed vial once cool. Oil will form separate layer.
  4. Use pasteur pipette to remove bottom oil layer (red-brown).

Video:

Characterization of Scoville Rating:

  • A panel of 5 volunteers tasted 1:10 serial dilutions of the original concentrate in 5% sucrose.
  • Spicy taste/sensation was noted at the 1:100 dilution by 4/5, and again at 1:10 with 4/5 (different individual as the negative result individual)
  • Concentrate was tasted after concluded to be safe enough to try – volunteers noted that the concentrate was comparable to tobasco sauce.

Future improvements:

  • Avoid the vacuum distillation process, as some capsaicinoids could have been lost at this step
  • Obtain better peppers, dry fully, and grind up well (this step was bypassed in lieu of filming the video quickly)
  • Perform TLC to determine composition of dilute extract and concentrate.

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