Rhodium chloride in a large glass/plastic container has a dark pink rose color, but, when in small amounts such as in the next image it is a very light pinkish peach color.

10x – Rhodium chloride in neck of a polypropylene pipette that will disperse drops onto glass slides to conduct this series of microchems.

10x – A drop of liquid Rhodium chloride on a glass slide was heated to dry, which caused these rings to form.

When heating Rhodium chloride the radiating vapors off the glass slide have a rather pleasant odor similar to, but exactly the same as Pd & Pt. In fact, the odor somewhat resembles that of delicate rose petals.

The heating of this solution was a little to aggressive , because the outer perimeter of dried solution blistered and cracked.

40x – A magnified view of the concentrated dried Rhodium chloride solution perimeter that I inadvertently heated too fast or too long.

Unlike other pgms Rhodium Chloride doesn’t seem prone to absorbing moisture from air (hydroscopic).

1 drop of concentrated HCl was placed on this dried area, which slowly went back into solution indicating that it does not self reduce like gold would under similar circumstances.

Note: when heating glass slides to force dry solutions, sometimes the glass will break. Therefore a good precautionary practice to avoid flying glass shards is to place the slide over a large towel and gently heat. Therefore. if too much heat breaks the glass the paper towel will catch both the solution and flying shards of glass.

10x – To the previous image of dried Rhodium chloride - concentrated HCl was added and a couple crystals of KI (Potassium Iodide) was inserted into the center of the pink solution.

Normally, if a precipitant is going to happen it does so rather quickly. However, nothing immediately occurred except for a slight yellowish area around the KI crystals. So, after a few minutes I gently warmed the underside of the glass slide containing the Rhodium chloride solution. Almost immediately a small amount of brownish area formed, which grew fast (couple of seconds) to what is shown in this image.

10x – The brown area in previous image quickly became this black area.

10x – The black area in previous image quickly became what is shown in this image.

40x – A magnified view of the crystalline perimeter at approximately the 7 o’clock position of previous image.
It appears that KI is a useful reagent in this particular circumstance.

10x – To the previous image of the dry solution a drop of concentrated HCl was added to see if anything would go back into solution. Even after considerable applied heat none of the blackish precipitants dissolved,.
To satisfy my curiosity – Aqua-Regia (1 drop HNO3 & 3 drops HCl) was placed in this dried area and with gentle heat everything dissolved and resumed the pink Rhodium color. No attempt was made to convert this A-R solution back to a chloride state.
Clearly, KI is a reagent that can precipitate Rhodium from a chloride solution.

10x – A potassium dichromate (K2Cr2O7) crystal was inserted into a drop of Rhodium chloride. No precipitant formed. The solution was heated to dry leaving this amorphous ring, which indicates that K2Cr2O7 is not a suitable reagent for indicating the presence of Rhodium in a chloride solution.

38x – A magnified view of the amorphous dry ring that the K2Cr2O7 in combination with Rhodium produced. Obviously there is no way that potassium dichromate is useful in helping to determine the presence of Rh in a chloride solution.

Because there are numerous reagents that can be utilized to aid in determining the presence of any element in any type of solution I have sometimes used chemicals that I knew was inappropriate, such as K2Cr2O7 in the previous microchem. Nevertheless, K2Cr2O7 was used just to show the prospector what would happen. Likewise, the next microchem using ammonium chloride is essentially valueless, but, because ammonium chloride was used to precipitate a complex salt of platinum it is again used here (next 3 images) to show the non-descriptive results.

10x –A crystal of Ammonium chloride was inserted into a drop of Rhodium chloride, which produced no precipitant. Thus, the solution was gradually heated to dry leaving this non-descriptive dried Rhodium salt.

40x – A white stage background was used in this magnified view of the dried ring of the inserted Ammonium chloride.
The only possible beneficial use of ammonium chloride is possibly the scarlet red ring which the microscope camera did not capture well.
This over-all pattern is somewhat typical of ammonium chloride in a variety of dissolved metals. Consequently, ammonium chloride is not worth the time spent for this particular test. However, if Pt and Rh were in the same chloride solution ammonium chloride would be beneficial to show the existence of one and not the other pgm.

40x – A black background microscope stage is used to illustrate a contrasting perspective of the dried ammonium/rhodium chloride solution.

The next 5 photomicrographs are of zinc powder added to a drop of liquid Rhodium chloride.

10x –A little bit of powdered zinc was inserted into a drop of Rhodium chloride solution, which caused an immediate reaction between the hydrochloric acid and zinc and better illustrated in next image.

40x – A magnified view of the preceding image showing the rather vigorous reaction of the zinc and hydrochloric acid as the Rhodium metal plates onto the zinc.

20x – The Rhodium is being cemented onto the zinc as shown in the darkened powder.

40x – When the reaction between zinc and acid has stopped one of three things has occurred – the zinc has totally been replaced with Rhodium, the zinc has consumed all the acid and/or the cementation process stops the acid from attacking the remaining zinc because the Rhodium encapsulates what zinc remains. Regardless of which scenario has played-out, normally there is always some zinc contamination.
When the solution is what I call quiet, the blackish cementation remains are removed then rinsed in concentrated HCL, which is followed by a water rinse. Next, the black flocculent is exposed to nitric acid bath and if no reaction the blacks go to another water rinse and dried. The dried blacks, depending upon what is desired are either exposed to high heat from a torch flame or Aqua-Regia for additional chemical tests.

10x – This toothpick tip was dipped into a drop of warmed Rhodium Chloride solution to be absorbed into the wood.
The toothpick tip is then ignited with the hottest part of a cigarette lighter flame.
This image shows a metallic tip and a brownish area then the blackened wood.
The brownish area near the tip is rich in metal, but has not been further exposed to more heat.

40x – A magnified view of the toothpick metallic tip, which in this case is known to be Rhodium because that was the only metal in the solution.