born of the prophet muhammad s favorite daughter , fatimah , al - hasan was declared as the legitimate successor of his father ,  ali ibn - abi - talib ( the last of the caliphs known to arab historians as  orthodox  ) , in 661 . faced by his rival , muawiyah ibn - abi - sufyan , who had been proclaimed caliph in 660 in jerusalem
, al - hasan abdicated in the same year and reasoned as follows :  i have deemed it right to make peace with him and have pledged allegiance to him , since i considered whatever spares blood as better than whatever causes it to be shed .  after living in retirement in al - madinah ( in present - day saudi arabia ) for eight years , al - hasan died in 669 , when he was just 45 years of age .
the belief that al - hasan died peacefully has not been ruled out by all the experts on muslim history .
however , in general , muslim theologians commonly believe that his death was caused by a fatal act of poisoning . with autopsy information
unavailable , historical documents are the only available evidence in order to investigate cases such as al - hasan s death scientifically . a few traditions , such as the one containing the following quote , mention that when al - hasan was about to die , he was asked by his younger brother al - husayn to identify his poisoner but refused to do so ( as he wanted no innocent person to be falsely accused and killed):if he / she [ the poisoner ] is not [ i.e. , not the one whom i suspect ] , i would like no innocent person to be killed because of me.still , the following tradition addresses two concurrent acts of poisoning , which resulted in two victims : al - hasan and a survivor . 

jadah daughter of al - ashath ibn - qays al - kindi poisoned al - hasan ibn-ali , peace be upon both of them , and poisoned a freedwoman of his ; however , the freedwoman of his vomited the poison while al - hasan kept it in his stomach .
this tradition says that a freedwoman of al - hasan who had also been poisoned  vomited the poison  and survived , which means that she could have served as forensic evidence for the murder of al - hasan . but are there any historical reports in which the poison is qualitatively described and can lead to a forensic hypothesis for the murder of al - hasan ? if he / she [ the poisoner ] is not [ i.e. , not the one whom i suspect ] , i would like no innocent person to be killed because of me . 

jadah daughter of al - ashath ibn - qays al - kindi poisoned al - hasan ibn-ali , peace be upon both of them , and poisoned a freedwoman of his ; however , the freedwoman of his vomited the poison while al - hasan kept it in his stomach .
that al - hasan was offered a poisoned drink by his wife jadah is reported in both shiite and sunni sources . since intoxicating drinks , such as wine , are not allowed in islamic law , the drink itself must have been a nonalcoholic drink . according to one tradition
one tradition describes the poison that was given to al - hasan as follows :  it has been said that he was given gold filings to drink .
elemental gold is relatively inert , and an important use for it is in dentistry .
it dissolves in concentrated hydrochloric acid if a strong oxidizing agent is present ( e.g. , in a 3:1 mixture of concentrated hydrochloric acid and concentrated nitric acid ) .
the hydrochloric acid in the human stomach is neither concentrated nor in the presence of a strong oxidizing agent .
what could the true identity of the toxic substance that al - hasan had ingested in the drink have been if the powdered solid phase of the substance only looked like gold filings ? in order to answer this question accurately , it is useful to know the geographic source of the poison .
the tradition referred to in the introduction , which says that a freedwoman of al - hasan had also been poisoned , suggests that the plot to poison al - hasan was because of some harem jealousy .
however , madelung says that al - hasan s  pursuit of women was not more covetous than that of most of his class .
 it is logically appropriate to ask if the murder of al - hasan could have had a political motive force behind it .
although al - hasan abdicated , in the process of surrendering the reign , he stipulated that his rival  should not be entitled to appoint his successor but that there should be an electoral council .  still
, when the caliph died in 680 , he had already  nominated his own son yazid as his successor  and caused homage to be paid to him .
there are reports , accepted by both shiite sources and several major sunni historians , stating that the poisoning of al - hasan by jadah was at the instigation of the caliph .
a very specific report says that in order to eliminate al - hasan , the caliph , whose empire s capital was damascus , wrote to the byzantine emperor and asked him for a poisoned drink , which the emperor , despite refusing at the beginning , sent conditionally .
the mention of the conditionality of the emperor s agreement in this report is consistent with the hostility of arab  byzantine relations in 669 ( the year al - hasan died ) , when byzantium had an energetic emperor , constantine iv .
the mainland of the byzantine empire in 668 ( about one year before al - hasan s death ) was approximately present - day turkey ( figure 1 ) .
in present - day western turkey , there are more than 50 mines that contain minerals with deposits of mercury .
mercury is isolated from its main ore , cinnabar ( mercury(ii ) sulfide , hgs ) , and was used in the mediterranean world for extracting metals by amalgamation as early as 500 bc .
the element does not have any known biological functions and has a long history of toxic effects .
mercury(ii ) chloride ( hgcl2 ) , for instance , which was probably first made by arabic alchemists in the 10th century , was widely used as a violent poison in the middle ages .
do the mercury mines in western turkey contain any mercury species that look like gold ? 

( chris ambrose , explore byzantium , http://byzantium.seashell.net.nz/ , is credited for the image . )
( chris ambrose , explore byzantium , http://byzantium.seashell.net.nz/ , is credited for the image . ) although abandoned since the 1990s , trkn and haliky are two important mercury mine locations in turkey .
the haliky mine exists in an area made up of metamorphic rocks , including gneiss and schist .
mine locations also contain deposits of pyrite , marcasite , chalcopyrite , arsenopyrite , quartz , and calcite .
the mineral calomel ( mercury(i ) chloride , hg2cl2 ) is found as a secondary mineral in oxidized zones along with cinnabar , calcite , and limonite .
calomel can present as a yellow gold crust ( figure 2 ) and forms as tetragonal crystals presenting in a variety of formations , including tabular , prismatic , and pyramidal . 

figure 2.calomel from mariposa mine , texas , usa . ( rob lavinsky , the arkenstone , www.irocks.com , is credited for the image . )
calomel from mariposa mine , texas , usa . ( rob lavinsky , the arkenstone , www.irocks.com , is credited for the image . )
the environmental assessments performed at the mine locations in turkey have utilized computer programs to aid in analysis of the soil and water samples .
the software programs aquachem and phreeqci determined that water samples taken near the haliky mine presented with oversaturation with calomel , as well as quartz and cinnabar .
without an autopsy or any diagnostic testing , it is impossible to diagnose with certainty what poisoned al - hasan .
however , we can hypothesize the type of poison used by the symptoms described in the traditions .
some clinical symptoms described by traditions of al - hasan s death are a green coloring of the skin and vomiting of blood .
these are also symptoms that can be caused by the ingestion of calomel and the resulting mercury intoxication .
calomel acts on the kidneys and causes renal tube necrosis and can lead to acute kidney failure .
the green coloring is due to a type of anemia called hypochromic anemia , also called chlorosis or green sickness .
this type of anemia is caused by a lack of hemoglobin , the oxygen binding protein responsible for nourishing our body tissues with oxygen .
hemoglobin is found within the erythrocytes or red blood cells , and a low erythrocyte count is the most common cause of hypochromic anemia .
if acute renal failure occurred , erythropoietin , the hormone that signals hemiopoetic stem cells in the bone marrow to have a cell fate of becoming erythrocytes , would not be present due to damage of the proximal renal tubule .
the promixal renal tubule is the area in which the red blood cell mass or hematocrit is determined by the kidneys .
it stands to reason that if the hematocrit level could not be correctly sensed due to renal tube necrosis , then the signal that is normally sent to the cortical labyrinth to make erythropoietin would be unlikely to occur .
the lack of this hormone would prevent new erythrocytes from being made , which in turn would result in a lower hemoglobin level , and a person affected by this would present with an ashen appearance , sometimes said to appear green .
the corrosive effects of calomel on the alimentary or gastrointestinal tract are known to cause damage and irritation of the esophagus .
kabid ,  an arabic word that means  liver  and also means  interior . 
if ulceration were to occur in the esophagus , a certain extent of bleeding should be expected .
when human blood reaches the stomach , it is broken down and can coagulate , very often resulting in vomiting a substance that has the appearance of coffee grounds .
this occurrence of vomiting blood is referred to as hematemesis and generally occurs due to esophagitis , bleeding ulcers , and certain cancers .
considering that the understanding of the human body in the 7th century was less extensive , the 
commoner s arabic expression  to refer to vomited blood clots would have been  kabid .
 in fact , in some rural areas in the arab world , it is still said ,  my liver is torn and thrust away ( kabidi mutaqatti ' mat'un ) .  in several traditions , al - hasan says that he is vomiting pieces of his  kabid ,  which could have been coagulated blood in the emesis , resembling pieces of his liver and/or internal organs due to the coffee - ground color and texture .
liver damage is another noted effect of mercury intoxication by calomel , which is due to the accumulation of deposits of mercury via the hepatic portal vein system .
this capillary type has the largest pores and is the only type that allows exchange of red blood cells through their pores .
red blood cells have susceptibility of the attachment of  corrosive sublimate  ( mercury(ii ) chloride , hgcl2 ) by way of a sulfhydryl attachment .
the liver is one of the areas where red blood cells are destroyed when they are damaged , which would allow for more mercury accumulation than the filtering of blood alone .
aqueous calomel ingested by the human body is converted into  corrosive sublimate ,  which is known to have much more harmful effects than calomel alone .
( hgcl2 ) , by oxidation in the hydrochloric acid ( hcl ) within the stomach .
this reaction , which is shown by equation ( 1 ) , goes to completion , as the calculated equilibrium constant for it , at the normal human body temperature ( 37 ) , is keq  =  2.4    10 . 

( 1)2hg2cl2(aq)+4hcl(aq)+o2(g )  4hgcl2(aq)+2h2o(l ) 
  calomel absorption into the body tissues is not seen in large quantities . however , it is enough to cause the anemia mentioned previously .
effects of  corrosive sublimate ,  such as intestinal ulceration , are thought to increase the amount absorbed due to the breakdown of protective barriers such as mucous membranes , which prevent absorption before damage .
noting that in the traditions al - hasan refers to being poisoned at least three times , if the initial poisoning had started this damage , the subsequent poisonings would have allowed a much greater amount of absorption of calomel or  corrosive sublimate . 
in later centuries , for example , when there was an outbreak of syphilis in europe at the end of the 15th century , calomel was routinely ingested as a medicine
. why could the calomel in al - hasan s drink have been lethal ? 

after the final poisoning , according to a couple of traditions , he says that he has been poisoned three times , and according to a few other traditions , he conveys the information that he has been poisoned at least four times . if the latter is the case , the number of times he was given calomel could have been too many to survive.according to one tradition , the final poisoning was when al - hasan was breaking his fast ( islamic fast , which includes refraining from eating and drinking from dawn to dusk ) on a hot day .
if that is the case , it will naturally lead to the conclusion that he ingested a large quantity of the drink containing aqueous calomel , which is  completely  converted to  corrosive sublimate  in the human stomach according to equation ( 1).the same net ionic equation as that of equation ( 1 ) ( equation ( 2 ) ) may be written for the reaction between any acids in the  to - be - ingested  nonalcoholic drink and the aqueous calomel in the drink , leading to the formation of mercury(ii ) , which is the mercury in  corrosive sublimate .
 a couple of examples of common arabic nonalcoholic drinks in the 7th century are honey water and yogurt drink , which both contain acids . 

( 2)2hg22+(aq)+4h+(aq)+o2(g )  4hg2+(aq)+2h2o(l ) 
 with the reaction shown by equation ( 2 ) in the  to - be - ingested  nonalcoholic drink , al - hasan has ingested some aqueous mercury(ii ) cation , in addition to the ingested aqueous calomel , which is converted to  corrosive sublimate  later ( in the human stomach , according to equation ( 1)).it is possible that the mineral calomel that was mixed with the drink was naturally accompanied by some other toxic substance(s ) .
after the final poisoning , according to a couple of traditions , he says that he has been poisoned three times , and according to a few other traditions , he conveys the information that he has been poisoned at least four times .
if the latter is the case , the number of times he was given calomel could have been too many to survive . according to one tradition ,
the final poisoning was when al - hasan was breaking his fast ( islamic fast , which includes refraining from eating and drinking from dawn to dusk ) on a hot day .
if that is the case , it will naturally lead to the conclusion that he ingested a large quantity of the drink containing aqueous calomel , which is  completely  converted to  corrosive sublimate  in the human stomach according to equation ( 1 ) .
the same net ionic equation as that of equation ( 1 ) ( equation ( 2 ) ) may be written for the reaction between any acids in the  to - be - ingested  nonalcoholic drink and the aqueous calomel in the drink , leading to the formation of mercury(ii ) , which is the mercury in  corrosive sublimate .
 a couple of examples of common arabic nonalcoholic drinks in the 7th century are honey water and yogurt drink , which both contain acids . 

( 2)2hg22+(aq)+4h+(aq)+o2(g )  4hg2+(aq)+2h2o(l ) 
 with the reaction shown by equation ( 2 ) in the  to - be - ingested  nonalcoholic drink , al - hasan has ingested some aqueous mercury(ii ) cation , in addition to the ingested aqueous calomel , which is converted to  corrosive sublimate  later ( in the human stomach , according to equation ( 1 ) ) .
it is possible that the mineral calomel that was mixed with the drink was naturally accompanied by some other toxic substance(s ) .
records of a green hue to al - hasan s skin , which could occur due to acute renal failure , concurrent with his vomiting of blood and , apparently , coagulated blood in the emesis are decisively consistent with those of calomel intoxication .
mineral calomel can present as a yellow gold crust ( figure 2 ) , which can , in the powdered solid phase , be mistaken for  gold filings  ( the identity of the poison according to a certain tradition ) .
the effect of al - hasan s poisoned freedwoman s recorded experience seems to indicate that contemporaneously to al - hasan s death , both people suffered the same affliction while residing under a common household .
this , in light of several historical sources , points at al - hasan s wife jadah as the prime suspect .
a considerable number of calomel - containing mercury mines exist in present - day western turkey , which was in the heart of the byzantine empire around the time of al - hasan s death .
the caliph sought to nominate his own son as his successor ( when the caliph died , he had done so and had caused homage to be paid to the son , who actually succeeded him ) .
al - hasan was obtrusively an obstruction to that goal , because that was despite the caliph s official guarantee of al - hasan s stipulation that he ( the caliph )  should not be entitled to appoint his successor . 
the report of the caliph s solicitation of the byzantine emperor by writing a letter asking the emperor for a poisoned drink is a clear example of his intent to act in furtherance of the plot , and , according to the report , the emperor s final response was a positive and deliberate agreement to that end .
the fact that neither an autopsy nor a judicial investigation was performed by the authorities at the time should not deter the use in evidence of eyewitness accounts .
mineralogical , medical , and chemical facts support the hypothesis that al - hasan s death was caused by calomel ( mercury(i ) chloride ) intoxication .
this forensic hypothesis is consistent with the historical position , reflected in ancient ( medieval ) documents , that al - hasan was poisoned by jadah , at the instigation of the caliph , and with the byzantine emperor s involvement .
the author(s ) declared no potential conflicts of interest with respect to the research , authorship , and/or publication of this article .
this research received no specific grant from any funding agency in the public , commercial , or not - for - profit sectors .
 the puzzle of a mysterious death in the middle ages has been hypothesized in terms of contemporary forensic legal and scientific methods . that al - hasan ibn-ali died in 669 aged 
 just 45 has been forensically analyzed based on written sources that dictate eyewitness accounts of historical events . 
 the report of the contemporaneous poisoning of another individual who resided under the same household as al - hasan s and experienced similar , yet non - lethal , symptoms has served as the beginning of the analysis . in light of ancient ( medieval ) documents and through using mineralogical , medical , and chemical facts , 
 it has been hypothesized that mineral calomel ( mercury(i ) chloride , hg2cl2 ) from a certain region in the byzantine empire ( present - day western turkey ) was the substance primarily responsible for the murder of al - hasan . 
Introduction
Gold filings or mineral calomel?
The symptoms in historical reports compared to those of mercury intoxication caused by ingesting calomel
Conclusions
Conflict of interest
Funding