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I need to make about 50 grams of soot (carbon black particles) in a high school laboratory. What would be the best way to do this?

The purpose of needing 50 grams of soot is because I would like to carry out an experiment that investigates how the percentage soot in oil (e.g. diesel) affects the viscosity of the mixture. To measure the viscosity, I would have to put 500 ml of oil in a measuring cylinder and do the ball-bearing method. The highest percentage I would like to test is 10% soot and that calls for around 50 g of it.

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    $\begingroup$ Soot and CB have a very diverse, and different, morphology. CB particles usually have an onion like structure. $\endgroup$ – Karl Apr 5 at 8:34
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There is an extensive literature on producing carbon black see for instance Donnet, Jean-Baptiste, ed. Carbon black: science and technology. CRC Press, 1993.

Instead of adapting the Roman recipe for producing lamp black explained on page 19, I would use olive oil rather than resin or turpentine (that is quite a nasty substance). For doing it on a small scale maximizing the yield maybe I would try (under the fume hood) to heat the oil in a flask attached to a water-cooled Liebing condenser after reaching the smoke point the soot should start to accumulate on the walls of the condenser. It should be quite easy to recollect the carbon black from the wall of the condenser with nylon bristle and maybe from a little funnel with a slight offset fixed on the exit of the condenser. All this should be carried out using heat-resisting glassware in a lab under the supervision of an adult.

P.S.

The highest percentage I would like to test is 10% soot and that calls for around 50 g of it.

This means that you will need more than 50 g for the whole experiment so if you test 10 different proportion you will need at least 80 g performing the experiment only once. It could require a lot of oil to produce 80 grams.

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It is not clear if your target is carbon black - there are commercial sources for this (e.g., here) - or soot. Ideally, composition wise speaking carbon black would be just carbon, while soot possibly is a blend of compounds, depending on what was partially burned, under which conditions (e.g., oxygen / carbon ratio, temperature, residence time in the reactor) assuming a continous flow reactor. But what about the reproducible distribution of shape and size of the particles?

Both automotive industry as well as raffineries know that viscosities of the oils depend e.g., on temperature, pressure and rotational speed (shear forces) of moving parts in an engine, as well as the composition of the oil / lubrificants used. Thus they use standarized test engines and test protocols to probe the endurance of these liquids (example). To ease exchange of the know-how in this field, CIMAC is one adress to retain. Beside a brief survey about oil degradation, abstracts of their database are available for non-members, too. Thus maybe CIMAC's PR office may assist in establishing a contact with a partner already performing such tests which is close to your area.

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Try burning turpentine.

It produces a very soot rich flame, per my recollection.

Another path per the article: Preparation of Carbon Nanoparticles from Candle Soot.To quote:

Carbon nanoparticles (CNPs) were prepared by simply mixing candle soot into ethanolic Nafion solution under ultrasonic radiation for 90 min. Well-defined CNPs could be obtained after centrifugation and washing.

[EDIT] My colleague mentions other choices for a school lab, citing benzene as a non-choice. The reason, let's hear from what the CDC says about it, to quote:

Immediate signs and symptoms of exposure to benzene.

People who breathe in high levels of benzene may develop the following signs and symptoms within minutes to several hours:

Drowsiness

Dizziness

Rapid or irregular heartbeat

Headaches

Tremors

Confusion

Unconsciousness

Death (at very high levels)

Another option suggested is toluene, comments from Toluene Safety Tips from MSDS experts – MSDSonline, to quote:

Toluene is a highly flammable liquid and it can cause mild damage to the skin and the eyes. However, the most-common hazard associated with this chemical is inhalation. Products containing toluene can produce dangerous fumes which can cause nausea, headaches, unconsciousness, and even death if inhaled.

Note, my final choice, for high school labs in general, is safe ordinary candle soot with a reference citing a preparation path to nanoparticles. Now, I could make other more potentially efficient and likely problematic suggestions, but I sleep well with this conservative/responsible choice.

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    $\begingroup$ Turpentine (pinene) has a C/H ratio of only 0.625, toluene is much better at 0.875, beaten by benzene (no good for a high school lab) and polystyrene, with a ratio of one. $\endgroup$ – Karl Apr 5 at 8:29
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    $\begingroup$ Thanks for the list of what I would not use in a high school lab (which you did note). Insurance cost and lab experiments gone wrong are likely good reasons for schools not to have chemistry labs, which can be mitigated, in part, by avoiding dangerous and toxic reagents in the hands of students. $\endgroup$ – AJKOER Apr 5 at 14:28
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    $\begingroup$ Well, smoke/soot is per se toxic if inhaled. What you cite for toluene is a default statement for any flameable liquid. Ethanol does the same, and certainly turpentine. $\endgroup$ – Karl Apr 5 at 15:01
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    $\begingroup$ Per a source: Candle soot can damage property, but has not been shown to have any adverse health effects. To keep a candle from sooting, make sure to trim the wick to ¼” before burning. Link: keapbk.com/blogs/keap/… $\endgroup$ – AJKOER Apr 5 at 22:10
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    $\begingroup$ Nobody should follow the unsafe and dangerous practices in this answer. $\endgroup$ – M. Farooq Apr 8 at 4:11

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