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English text reference: Chinese Pharmacopoeia (2020 Edition)

Overview

Calomel is the chloride of mercury (Hg2Cl2).

Description

Calomel occurs as white, lustrous, scaly or snowflake-like crystals, or as crystalline powder. It darkens slowly on exposure to light. Odour, slight.

Identification

(1) When tested with calcium hydroxide solution, ammonia solution or sodium hydroxide solution, it turns black.

(2) Take the product, mix it with an equal amount of anhydrous sodium carbonate, place it in a dry test tube, heat it, and metallic mercury is decomposed and condensed on the wall of the test tube. Dissolve the residue remaining in the tube in dilute nitric acid, filter, and the filtrate shows the identification reaction of chloride (General Rule 0301).

Examination

Mercury

Take 2 g of the product, add 20 ml of ether, shake for 5 minutes, filter, evaporate the filtrate to dryness, dissolve the residue in 10 ml of water with 2 drops of dilute nitric acid, and examine according to the method for chloride (General Rule 0801). If turbidity occurs, compare it with a control solution prepared in the same manner using 7 ml of standard sodium chloride solution, and it should not be more turbid.

Mercury beads

Take about 1 g of the product, spread it on white paper, and examine it with a magnifying glass. There should be no mercury beads.

Residue on ignition

Not more than 0.1% (General Rule 0841).

Assay

The sample, about 0.5 g, is accurately weighed, placed in an iodine flask, and 10 ml of water is added. The mixture is shaken well, and then 50 ml of iodine titration solution (0.05 mol/L) is accurately added. The flask is stoppered, and the mixture is vigorously shaken until most of the sample is dissolved. Then, 8 ml of potassium iodide solution (5→10) is added, the flask is stoppered, and the mixture is vigorously shaken until completely dissolved. The solution is titrated with sodium thiosulfate titration solution (0.1 mol/L) to near the end-point. Starch indicator solution is added, and the titration is continued until the blue colour disappears. Each 1 ml of iodine titration solution (0.05 mol/L) is equivalent to 23.61 mg of mercury chloride (Hg2Cl2).

The content of mercury chloride (Hg2Cl2) in the product shall not be less than 99.0%.

Property

Cold.

Toxicity

Toxic.

Flavor

Pungent.

Meridian tropism

Large Intestine and Small Intestine meridians.

Actions

To kill parasites, counteract toxicity, promote wound healing when used externally; to resolve phlegm, eliminate accumulation, promote diuresis, and facilitate bowel movement when taken internally.

Indications

It is used externally for scabies, ringworm, poliomyelitis, syphilis, sores and eczema; internally for phlegm and saliva stagnation, oedema and swelling, and bowel problems.

Dosage

Appropriate amount for external use; 0.1～0.2g each time for internal use, 1～2 times a day.

Administration

Ground and mixed with the affected area; more into the pill or capsule service, gargling after service.

Precautions

This product is toxic and should not be taken in excessive amounts. It should be used with caution when taken internally, and it is contraindicated in pregnant women.

Storage

Store in a light-resistant, airtight container in a dry place.

轻粉

Text reference: Chinese Pharmacopoeia (2015 Edition)

Overview

Calomel is a mercurous chloride (Hg2Cl2).

Description

White, lustrous, scaly or snow-flake like crystals, or a crystalline powder. Gradually darkened on exposing to light. Odour, slight; almost tasteless.

Identification

（2）取本品，加等量的无水碳酸钠，混合后，置干燥试管中，加热，即分解析出金属汞，凝集在试管壁上，管中遗留的残渣加稀硝酸溶解后，滤过，滤液显氯化物（通则0301）的鉴别反应。

Examination

Mercuric chloride

Shake 2 g of the drug in 20 ml of ether for 5 minutes, filter, allow to stand and expel the ether. Dissolve the residue in 10 ml of water and 2 drops of dilute nitric acid TS, carry out the limit test for chlorides <0801>. Any turbidity produced is not more intense than a reference solution prepared with 7 ml of standard solution of sodium chloride.

Mercury globule

Spread 1 g of the drug on a piece of white paper, examine under a lens, no mercury globule should be found.

Residue on ignition

Not more than 0.1 per cent <0841>.

Assay

To about 0.5 g of the powder, accurately weighed in a stopper flask, add 10 ml of water, shake well,add 50 ml of iodine (0.1 mol/L)VS, accurately measured, stopper tightly, shake vigorously until most of the powder dissolved, add 8 ml of potassium iodide solution (5→10), stopper tightly, shake vigorously to dissolve completely, titrate with sodium thiosulfate (0.1 mol/L) VS towards the end of titration, add starch IS,continue to titrate until the blue colour disappeared. Each ml of iodine (0.1 mol/L) VS is equivalent to 23.61 mg of HgeCl. It contains not less than 99.0 per cent of mercurous chloride (Hg2Cl2)

Property and Flavor

Cold; pungent； toxic. Meridian tropism: Large intestine and small intestine meridians.

Actions and Indications

Topical application: To kill worms, conteract toxic substances, and promote wound healing；Oral administration: To dispel phlegm, relieve accumulation, expel water and open the bowels.

Indications

Topical application: scabies, stubborn tinea, shank sore, syphilis, sore and ulcer, and eczema; Oral administration: excessive phlegm and saliva, edema,tympanites, inhibited defecation and urination.

Administration and dosage

Appropriate amount for topical application, ground into powder for applyment; Oral administration: 0.1-0.2 g per time, 1-2 a day, usually used in pills or capsules, gargling after oral administration.

Precautions and Warnings

Poisonous, avoid overdosage. Be cautious for oral administration. Contraindicated for pregnant woman.

Storage

Preserve in a well closed container, and protect from light and stored in a dry place.