Do you know what solutions and suspensions are and how to tell them apart? Basically, solutions are homogeneous mixtures where the components stay mixed. The components of a suspension separate on their own, though you can mix them to make the substance homogeneous for a while. You can form a solution by dissolving sugar in water. You can form a suspension by stirring corn starch into water.

The particles in dispersions are intermediate in size between those of solutions and suspensions. Dispersions can remain evenly mixed, like suspensions, but dispersions exhibit the Tyndall effect, which means light passing through them will be scattered by the particles so that the light beam is visible.
Learn More | Liquids Magnets: Colloid Example

September 10^th is Waldo Semon's birthday. Semon was an American chemical engineer who discovered the process to make vinyl from polyvinyl chloride or PVC. He was working for the BF Goodrich chemical and rubber company to find an adhesive to bond rubber to metal and working with the polymer polyvinyl chloride. PVC in its raw form is a rigid and brittle material with little to no functional use. Semon did not find the adhesive he was searching for, but he did find out a combination of solvents and boiling would turn PVC into a flexible, elastic plastic. Plasticized PVC would become one of the most important and mass produced plastics in use today. It is used in many different construction applications like wiring insulation and plumbing. It is estimated that in the US alone, PVC tubing accounts for up to 75% of plumbing.

Thanks, Waldo! Find out what else occurred on this day in science history.

Potassium chlorate (KClO₃) is one of the most useful potassium compounds you can keep around the chem lab. It can be used as an oxidizer and disinfectant and to make pyrotechnics, safety matches, and to prepare oxygen gas. You can prepare potassium chlorate from common household chlorine bleach and salt substitute. The reaction is not particularly efficient, but it's something to keep in mind if you need potassium chlorate right away or just want to know how to make it.

Materials for Making Potassium Chlorate

• chlorine bleach
• potassium chloride (sold as a salt substitute)
• filter paper or coffee filter

Prepare Potassium Chlorate

1. Boil a large volume (at least a half liter) of chlorine bleach, just until crystals start to form. Do this outdoors or under a fume hood, to avoid inhaling the vapor. Boiling bleach disproportionates sodium hypochlorite into sodium chloride and sodium chlorate.

   3 NaClO → 2NaCl + NaClO₃

2. As soon as crystals start to form, remove the bleach from heat and allow it to cool.

3. In a separate container, prepare a saturated solution of potassium chloride by stirring potassium chloride into water until no more will dissolve.

4. Mix equal volumes of the boiled bleach solution and potassium chloride solution, taking care to keep solids from either solution out of the mixture. Potassium chlorate will precipitate out, leaving sodium chloride in solution.

   KCl + NaClO₃ → NaCl + KClO₃

5. Cool the solution in the freezer to increase the potassium chlorate yield.

6. Filter the mixture through filter paper or a coffee filter. Keep the solid potassium chloride; discard the sodium chloride solution.

7. Allow the potassium chlorate to dry before storing or using it. NurdRage has a video of the process, if you'd prefer to see how it's done.

You can test the potassium chlorate in a simple chemistry demonstration:

• Purple Fire (shown) - Mix potassium chlorate and half as much sugar. Ignite the mixture either by applying a flame or adding a few drops of sulfuric acid (instant chemical fire).

• Dancing Gummi Bear - The candy is the source of the sugar in this demonstration. The vigorous reaction between the candy bear and the potassium chlorate makes the bear appear to dance in purple fire.

On September 9, 1947, Grace Hopper discovered the first computer bug. She was working as an operator on the Havard Mark II computer when the operators were attempting to trace a problem in the hardware. Wedged into Relay #70 on Panel F was a large moth's body and causing a short circuit. Hopper recorded and taped the find in the logbook as "The first actual case of bug being found".

This story is the source of many legends. One legend involves the year the bug was found. Most versions, including the Navy's history, has the event taking place in 1945, others, in 1947. Grace Hopper began work on the Mark II computer in 1945 and stayed at Harvard until 1949. The Smithsonian catalog records the date as 1947.

Another common legend has this story as origin of the term 'bug' to mean an error in the system. Bugs have been an engineering term for many years. Edison was quoted in 1878 using the term bugs to refer to problems arising in the engineering process. This was the first 'computer' bug and is often cited as the origin of the term 'debugging' to fix computer issues.

One last legend concerns the location of the now famous log entry, complete with moth. Most stories has the log page on display at the Smithsonian or the Naval Surface Warfare Center Computer Museum in Dahlgren, Virginia. The log was originally kept at the Naval museum but it is now on display at the Smithsonian National Museum of American History.

This story is a fun piece of early computing folklore. Find out what else occurred on this day in science history.