Forensics - SciOly 2020

Sodium flame

yellow flame, very distinct.

• will contaminate other compounds EASILY

Lithium flame

carmine or red flame

Calcium flame

yellow-red flame

Boric Acid flame

bright green flame, very visible

Ammonium Chloride flame

faint green flame

Potassium flame

light purple, lavender flame

Tests with liquids

liquids used for identification are iodine, sodium hydroxide, hydrochloric acid, Benedict's solution, and water.

• not all liquids are applicable to all samples.

Iodine

When _____ is added to cornstarch, the sample will turn black. If cornstarch is not present, the _____ will remain brown.

Sodium Hydroxide

_____ ________ is used simply to categorize your samples into two fields: NaOH reactive- and non-reactive. For this reason, it is extremely useful when using a flowchart.

• To perform this test, a few drops of NaOH is added to a small sample of chemical dissolved in water. If a milky-white precipitate forms, the sample is NaOH reactive. If a precipitate does not form, the sample is NaOH non-reactive.

Hydrochloric Acid

________ ____ will react when added to samples containing carbonates--therefore, it is useful in identifying calcium carbonate, sodium carbonate, and sodium hydrogen carbonate.

Benedict's solution

_________ ________ is used to detect glucose.

• To perform this, dissolve a sample of a chemical in water in a test tube. Add two to three drops of ______ _______, then place the test tube in a hot water bath.

• If glucose is present, the sample forms an orange precipitate.

• Sucrose will not react with _______ ________ but glucose will.

• Can also be used to test for ammonium chloride. Adding a couple drops will turn the sample a dark blue.

Water

_____ is used for determining the solubility of chemical samples, and is used for making solutions.

pH

The __ data for chemicals can be useful, especially for determining between two similar chemicals. Most samples have a __ of between 5 and 7, but there are several chemicals that have distinct ___

Conductivity

Certain chemical samples will dissociate and become conductive when dissolved in water.

• To perform this test, dissolve a small sample of dry chemical in water.

• Using a 9-volt conductivity tester will determine whether a sample is conductive or semi-conductive.

Solubility

All samples can be divided into two fields--soluble and non-soluble.

• Water is used to perform this test.

Soluble Samples

sodium acetate, sodium chloride, sodium hydrogen carbonate, sodium carbonate, lithium chloride, potassium chloride, calcium nitrate, glucose, sucrose, magnesium sulfate, boric acid, and ammonium chloride.

Non-soluble Samples

calcium sulfate, calcium carbonate, and cornstarch

Polystyrene (PS)

Yellow flame

• Burns quickly

• Plastic drips

• Illuminating gas odor (naphtha)

• Dense black smoke w/ soot (floating particles)

• CD / DVD jewel cases

• Audio and videocassette casings

• Model assembly kits

• Clear disposable cups

• Styrofoam packaging such as boxes, filler material, etc (EPS)

• Styrofoam tableware such as cups, plates, containers, etc (EPS)

• Building insulation (EPS)

• Cases for electronic equipment such as television, air conditioner, and computer cases (HIPS)

• Stationary such as pen cases, organizing trays, etc (HIPS)

• Toys (HIPS)

Polypropylene (PP)

• Blue, yellow tipped flame

• Burns slowly

• Plastic drips

• Has sweet odor

• Floats in water

• A common use of PP is in food containers. PP is naturally BPA free and has a high melting point making it dishwasher and microwave safe.

• Due to its resistance to fatigue, most hinge type products are also made from PP (such as flip-top bottles, lock&lock Tupperware, etc…).

• PP is often used for storage containers such as Rubbermaid and Sterilite containers. The softer, rubbery lids are made of a softer plastic, usually LDPE.

• Products made from PVC and HDPE can also be made with polypropylene. For instance, the infamous PVC piping can also be manufactured using PP. HDPE furniture such as tables and chairs can also be substituted using PP.

• PP is commonly used in non-woven fabrics (used in diapers and or sanitary products).

• Polypropylene is commonly used for producing ropes, carpets and recycled plastic rugs.

• Many stationary products such as plastic folders, notebook covers, paper protectors, storage boxes are also made from PP. These products are made through the plastic extrusion process.

Polyvinyl Chloride (PVC)

• Yellow flame w/ green spurts

• Plastic does not drip

• Self extinguishing

• Smells like hydrochloric acid

• Plastic chars

• A large usage of flexible PVC is in wire insulation (colored plastic wrapped around electrical wires). Flexible PVC can be found in clothing such as raincoats, rain boots, and leather-like fabrics. PVCs are also made into vinyl records and vinyl signs and billboards.

• About 75% of all PVC resin (rigid) is made into construction materials such as piping & fittings, siding, flooring, windows, fencing, decking, roofing, wall coverings, etc

Low Density Polyethylene (LDPE)

food containers (specifically bags), grocery bags, plastic wrap, etc.

High Density Polyethylene (HDPE)

food containers, bags, lumber, furniture, flower pots, signs, trash cans, toys

Polycarbonate (PC)

• Orange flame

• Self extinguishing

• Plastic drips

• Black smoke w/ soot (floating particles)

• Faint, sweet aromatic odor

• Data storage including, CDs, DVDs, blu-ray discs, etc…

• Lenses including sunglasses, prescription glasses, automotive headlamps, riot shields, instrument panels, etc

• PC is derived from bisphenol A (BPA) and is no longer used in food applications

• Electrical and telecommunications hardware

• Construction materials such as dome lights, sound walls, etc

• Automotive, aircraft, and security components

• Medical applications

Polyethylene Terephthalate (PET or PETE)

• Yellow flame

• Plastic drips

• Burns slowly

• light smoke

• Polyethylene Terephthalate is probably most well known for its use in water, juice, and soda bottles. You’ll also find PET plastic used in other packaging such as peanut butter jars, containers for holding salad dressings, cooking oils, cosmetics, and household cleaners. PET used for plastic packaging consumes roughly 30% of PET usage worldwide.

• A major use of Polyethylene Terephthalate is in synthetic fibers used for manufacturing polyester clothing, fabrics, carpets, etc. PET used for this purpose consumes more than 60% of PET usage worldwide!

Polymethyl Methacrylate (PMMA)

Plexiglas, glass substitute

Wool

• Animal

• Most commonly used animal fiber

• shrivels, leaves brown-black residue, smells like burning hair

• cylinder with scales

Silk

• Animal

• Smoother than wool

• shrivels, leaves black residue, smells like burning hair

• thin, long and smooth cylinder

Cotton

• Vegetable

• Most widely used plant fiber, fairly short fibers

• burns with a steady flame, smells like burning paper, able to blow flame from thread like a match, leaves a charred whitish ash

• irregular twisted ribbon

Linen

-Vegetable

• fibers generally longer and smoother than cotton

• burns at a constant rate, does not produce smoke, smells like burning grass, produces sparks

• smooth, bamboo like structure

Polyester

• Synthetic

• fibers can be any length

• melts, only ignites when in the flame, drips when it burns and bonds quickly to any surface it drips on, produces sweet odor and hard, colored (same as fiber) ash

• completely smooth cylinder

Nylon

• Synthetic

• long fibers

• curls, melts, produces black residue, smells like burning plastic (some sources say it smells like celery?), ignites only when brought into flame

• fine, round, smooth, translucent

Spandex

• Synthetic

• can stretch to eight times its original length

• melts quickly

• Flattened, ridged fibers, clustered