Would it be possible for the authors to include a section on compliance with ethical standards to the end of this manuscript. A suitable section for this paper would be (if there are indeed no conflicts of interest and no studies with human or animal subjects):
Review by Jaclyn Catalano
This review was submitted on 04 January 2017, and refers to this previous version of the article
Sections reviewed: Abstract, Physical Properties, Chemistry, Application and Biological effects
Overall, good overview of lead and numerical values for the physical properties of lead are
The facts are correct. Good overview of lead.
1. Inconsistency between the color described in the abstract and the section Physical
- Abstract: When freshly cut, lead is bluish-white;
- Physical Properties, Bulk: Pure lead has a bright silvery appearance with a hint of blue.
2. Lead is more than a neurotoxin. This sentence could be rephrased, Lead is
a neurotoxin that accumulates in soft tissues and bones, damages the nervous system,
and causes blood disorders.
Rephrased: Lead is a toxin that accumulates in soft tissues and bones, it acts as a
neurotoxin damaging the nervous system and interferences with the function of
3. It is particularly problematic in children: even if blood levels are promptly normalized
with treatment, permanent brain damage may result.
Instead of Permanent brain damage. Rephrase to neurological disorders, such as brain
damage and behavioral problems.
4. See comment above about the color. Also if it tarnishes it is subjected to corrosion.
5. It tarnishes on contact with moist air, and takes on a dull appearance the hue of which
depends on the prevailing conditions. Characteristic properties of lead include
high density, malleability, and high resistance to corrosion (due to passivation).
Remove the bracket in the sentence above (due to passivation). Tarnishing is a
form of corrosion so it is important that the corrosion discussed in the following
sentence is due to passivation.
6. Organic acids, such as acetic acid, dissolve lead in the presence of oxygen.
Rephrase to: Organic acid, such as acetic acid dissolves lead in the presence of oxygen to
and forms the corresponding lead salt in solution, such as lead (II) acetate.
Lead (II) compounds
7. Include the names for alpha-PbO and beta-PbO.
Rephrase: Lead monoxide exists in two polymorphs, Litharge α-PbO (red) and Massicot
β-PbO (yellow), the latter being stable only above around 488 °C. (I would also include
the hyperlink to Lead monoxide and the respective lead isoform pages)
8. Lead paint should be added. (Some of this information is in the Modern Era Section)
9. Is there a reference for this “Only about a third of lead is excreted by a child.”
10. Include a sentence on lead inhibiting the enzyme (ALAD) that synthesizes heme.
11. Ingestion of applied lead-based paint is the major source of exposure for children: a direct
source is chewing on old painted window sills.
Include also, and peeling paint chips.
Review by anonymous peer reviewer
This review was submitted on 06 January 2017, and refers to this previous version of the article
Sections reviewed: Abstract, Physical properties, Chemistry, Etymology, Production, Applications
First sentence – lead isn’t “assigned” atomic number 82. It simply has atomic number 82 by definition. Perhaps “Lead is a chemical element, with atomic number 82, that is assigned …”.
Second paragraph, second sentence: “lead and lead oxides…., and it…”. “It” has an unclear antecedent and should be replaced by the word “lead”. Third paragraph, fourth sentence: there should be a comma after “ductility”. In the pdf version I received, the last paragraph of the abstract is in a different font size than the rest of the abstract.
first paragraph, last sentence. I’d like to see the inert pair effect clarified so the reader understands it is limited to post-transition metal elements. Also, at the end of that sentence, it seems strange to use the word “long” to describe a distance. I believe “large” would be more appropriate. However, it doesn’t seem to me that any aspect of crystal structure belongs here, since the rest of the paragraph focuses on ionization energies. Finally, “become reluctant to” seems like an anthropomorphism to me, which should perhaps be avoided. Perhaps this sentence should read “Due to the inert pair effect observed in post-transition metal elements, the 6s electrons of lead are relatively more unlikely to engage in bonding than expected based on periodic trends, leading to increased ionization energies and favoring the +2 oxidation state”. The part about the large distance between nearest atoms in crystalline lead should be shifted to the next paragraph.
the table about isotopes belongs in the next section.
First paragraph – commas should be added after “bright” in the first sentence and “appearance” in the second sentence. Lead is ductile, so that should be added to the list of characteristics: “…malleability, ductility, and high resistance…”
Last paragraph, third sentence – the word “at” should be added after “gold”.
Should there be a source/citation for “nuclear shell model” in paragraph 1? I think the table about isotopes belongs here, with a comment, and the sentence immediately under the paragraph needs to be worked in here. I’d recommend the second sentence in this paragraph should be something like: “The main isotopes of lead, with information on percent abundance, half-life, and decay mode and product, are listed in Table 1, although isotope abundances vary greatly by sample.”
In the third paragraph, third sentence, “Their isotopic concentration” needs to be changed to “Their isotopic concentrations”. In this same paragraph, the ratios used in lead-lead dating need to be clarified. I suggest the second-to-last sentence should have the last phrase removed (“this allows for lead-lead dating”). Another sentence should be added after this one, reading something like “Lead-lead dating involves analysis of lead-207/lead -204 ratios versus lead-206/lead-204 ratios.”
One important application of a specific lead isotope is missing: Lead-207 is NMR-active, which has led to a huge and important field of research and has medicinal applications. There ought to be at least one reference to this body of knowledge.
First paragraph, second sentence – the name should be lead(II) carbonate. Second paragraph, second sentence needs a comma after “heating” - “…requires heating, as the resulting…”
Third paragraph, first sentence – “insolubility” would be better changed to “solubility”
First paragraph, second sentence; rather than just “… the more important for lead”, for clarity consider “the more important of the two oxidation states for lead.” Fifth sentence, rather than “This is less applicable…”, substitute a specific word for “this”, such as: “The inert pair effect is less applicable…”. In the same sentence, place a comma after “electronegativity”.
Second paragraph, last sentence requires a “the” added before “carbon” (“…going down the carbon group…”)
First paragraph, second sentence – the second listed hydrolysis product is incorrect: it should be [Pb4(OH)4]4+. Also, this is not the final product, but the most common one. The sentence would be more accurately changed to:
- “Lead(II) ions are usually colorless in solution. No simple hydroxide is found; in aqueous solution, the lead(II) ion undergoes a series of pH-dependent hydrolysis and condensation reactions, including Pb(OH)+ and the most common hydrolysis product, [Pb4(OH)4]4+. ,” (These are not the original references. I was unable to access reference 49, but I did use sources 50 and 52 for checking these facts).
I was unable to check reference 51 about the qualitative analysis of lead in the last two sentences of the first paragraph. The last statement needs to be checked, I believe. To my best knowledge, lead(II) chloride is sparingly soluble in cold water, not somewhat soluble. The precipitation of lead(II) chloride using dilute hydrochloric acid will detect the presence of lead in all but extremely dilute solutions. The last sentence makes it seem as if hydrogen sulfide is bubbled through the solution when it has already been treated with dilute hydrochloric acid. This makes no sense, because at that point almost all of the lead will be present as a precipitate and will not react. So I believe the last sentence should be changed to “As the chloride salt is sparingly soluble in water, in very dilute solutions the precipitation of lead(II) sulfide is achieved by bubbling hydrogen sulfide through the solution.”
Second paragraph – The proper name is lead(II) oxide; “lead monoxide” should be avoided. It would enhance the first sentence to add the common names of the two forms of PbO: “… red a-PbO (litharge) and yellow b-PbO (massicot)…”. The use of the word “it” is very confusing. The second sentence needs to specify which form. Either “Litharge” or “a-PbO” needs to replace “It” in that sentence. Also, as written, the sentence is untrue: tetraethyl lead is the most commonly used lead compound. So the second sentence should be changed to read: “Litharge is the most commonly used inorganic compound of lead.”
The third sentence of the second paragraph is confusing and likely inaccurate; I can’t access reference 53. I’m not sure what is meant by the hydroxide “counterpart” of lead(II) oxide. The hydroxides have already been discussed in the first paragraph. As far as plumbite, I THINK that it is produced by hydrolysis in weakly basic solutions; strongly basic solutions would result in plumbate.
In the third paragraph, the next-to-last sentence could use some elaboration – a few examples of the lead pseudohalides that are known should be listed.
In this paragraph, all names should be stated in proper (IUPAC) format: Lead(IV) oxide, lead(II) oxide, lead(IV) oxide, lead(IV) sulfide, lead(IV) selenide, lead(IV) fluoride, lead(II) fluoride, lead(IV) chloride, lead(IV) bromide, and lead(IV) iodide.
An important lead(IV) compound is omitted: Lead(IV) acetate is a well-known, selective oxidizing agent.
iii. Other oxidation states
In the first paragraph, second sentence, a comma needs to be added for clarity: “… this oxidation state is not stable, as both the ….” The next sentence is unclear: what is meant by “such species”? There needs to be some follow-up – “… in such species as…” or perhaps “in similar organolead complexes to the lead(III) complexes” if that’s the case (I can’t access reference 67 to check this).
In the second paragraph, third sentence, Pb2O3 needs to be set off with commas before and after.
In the first paragraph, first sentence, all members of the group have the ability to form multiply-bonded chains (note the hyphen between “multiply” and “bonded”). The first two sentences should be replaced with: “Lead can form multiply-bonded chains, a property it shares with the lighter members of Group IV. The capacity for catenation decreases going down the group due to decreasing bond energy. The Pb-Pb bond energy is…”
third sentence, for clarity, add a comma after “itself”.
Next to last sentence – again avoid the unclear “it”. Try: “Lead forms predominantly organolead(IV) compounds, even when starting…”
In the second paragraph, plumbane is unstable; this should be stated, probably in a third sentence: “Plumbane itself is thermally unstable, but is used to obtain a variety of alkyl derivatives.” In the next-to-last sentence, lead(IV) acetate should be used rather than lead tetraacetate; also, I think it would be worthwhile noting WHY tetraethyllead was produced in such large quantities: “…in larger quantities than any other organometallic compound, due to its widespread use as a gasoline additive.” In this same sentence, there should be a comma after “organic chemistry” and “chemistry” should be changed to “synthesis”.
First paragraph, sixth sentence (“According to…”) requires a comma after “discarded”
Second paragraph: “primary” and “secondary” describe the process, not the metal. So the first sentence should read “The primary and secondary lead production processes are similar.”. The third sentence also needs to be modified: “Given adequate techniques, lead obtained via secondary processes is indistinguishable from lead obtained via primary processes.”
i. Two-step process
the chemical equations ought to contain phases (PbS(s), for example). In the second sentence, oxides of other metals are also generated in the roasting process, but the wording does not indicate this. Consider changing to “…roasting yields not only the desired lead(II) oxide, but a mixture of oxides, sulfates, and silicates of lead and of the other metals…”
The second-to-last sentence in this paragraph needs clarification: the Parkes process relies on the immiscibility of zinc in lead, not of silver or gold in lead.
Perhaps change to: “The zinc, which is immiscible in lead, dissolves the silver and gold. The zinc solution can be separated from the lead, and the silver and gold retrieved.”
Another issue I’d like to see clarified is whether the Betts process is regularly employed when very pure lead is required. The mention of electrolysis in the “alternatives” section makes it seem as if electrolysis is not currently widely used, but I believe it is common when very pure lead is required.
ii. Direct process
In this section, the proper name of “lead monoxide” is lead(II) oxide.
In the first paragraph, the first sentence should have a comma after “In this process,…” In the second sentence, the parenthetical expression should begin with “as”: “Carbon (as coke or coal gas)…”
In the second paragraph, I think it should be specified that the form of lead in the high-lead slag mentioned in the second sentence is lead(II) oxide.
Hydrometallurgical extraction is a much broader term than implied here; several different methods may be used, rather than just electrolysis.
In the second sentence, it’d be nice to see numbers to back up the statement about the variability of yields. In the last sentence of this paragraph, the last phrase is confusing: are bismuth and silver being accepted as impurities, rather than trying to remove them? Or is it understood that bismuth and silver are the most common impurities?
Begin the third paragraph with the word “Lead” rather than “Its”. In the third paragraph, the third sentence, the word “weight” is inaccurate. Perhaps combine the second and third sentences: “It is used as ballast in sailboat keels; its density allows it to take up a small volume and minimize water resistance, thus counterbalancing the heeling effect of wind on the sails.
In the fifth paragraph, the second sentence requires a comma after the word “copper”.
Reviewer-annotated pdf file
Review by Robert M. Gogal Jr.
This review was submitted on 12 January 2018, and refers to this previous version of the article
Sections reviewed: Environmental effects, Restriction and Remediation
1. Change to... The extraction, production, use, and disposal of lead and its products have resulted in significant contamination of the Earth's soils and waters. Atmospheric emissions of lead were at their peak during the Industrial Revolution and the second half of the twentieth century with the use of leaded gasoline for automotive transportation.
2. Elevated concentrations of lead persist in soils and sediments in post-industrial and urban areas; industrial emissions, including those arising from coal burning, continue in many parts of the world, particularly in the developing countries. ...... This statement leaves the reader thinking that lead contamination is solely a result of industrial contamination, which it is not.
3. The fact is that particulate lead in the form of spent shot and fragments from recreation shooting ranges, military ranges and sites of active and past military conflicts contain significant levels of lead in the soil. It has and still is a major health problem to humans and wildlife. Although there has been much effort to reduce the use of particulate lead in ammunition in industrialized nations it is still utilized in third world countries. I
recommend that the author add 3-4 sentences about particulate lead to this sub-section.
4. Change to... Environmental lead can compete with other metals found in and on plants surfaces potentially inhibiting photosynthesis and at high enough concentrations, negatively affecting plant growth and survival.
5. Change to... Contamination of soils and plants can allow lead to ascend the food chain affecting microorganisms and animals.
6. Affected animals have a reduced ability to synthesize red blood cells, which causes anemia. .....This sentence seems out of place or incomplete to me.
7. Lead is a neurotoxicant in wildlife species as well as man. In addition to hemo, it is a renal, repro and hepatotoxic. The author would do well to follow the review of the biological effects similar to man for wildlife species if he wishes to comment on environmental effects of lead.
8. There have been numerous studies on the effects of lead on marine species and avian species (aquatic and terrestrial). I would recommend a sentence being included regarding this issue. The author’s the statement that lead "reduced ability to synthesize red blood cells, which causes anemia" is not entirely accurate. Lead has been shown to block heme synthesis leading to a decline in RBC survival and increased hemoloysis.
9. An important biomarker assay for lead exposure is measuring delta aminolevulinic-acid dehydratase (d-ALAD) and both serum and urine samples are commonly collected for evaluation.
Restriction and remediation
Verb tense needs to be changed to the past tense throughout this section where appropriate
1. Change to... By the mid-1980s, there was significant decline in the use of lead in industry.
2. Change to... Particulate control devices were installed in coal-fired power plants to capture lead emissions.
3. The author starts with discussing the shift in industrial lead use in the 1980s and discussing government regulations as the driving force. Then, he changes verb tense on the following sentences. Beyond the first couple of sentences, it is hard to discern what regulations and restrictions are past and which ones are newly enacted although, I suspect that many of them are regulations that were enacted in the past. Perhaps, the author can heavily revise this section?
4. The last sentence in the first paragraph discusses the 1993 Netherland’s ban on lead shot and the decline in environmental lead in tonnes. If the referenced paper is about particulate measured, it should be “deposition” and not emission.
5. Last paragraph is a loose compilation of sentences that are not very well unified. I would recommend a heavy revision of this paragraph as well.
6. The remediation discussion paragraph should also include the efforts to control and minimize the effects of environmental particulate lead. In addition to using lead capture nets and backstops, the Environmental Protection Agency (EPA) in 2005 published a guideline entitled, Best Management Practices for Pb at Outdoor Shooting Ranges, outlining management protocols for more sustainable and safe management of spent Pb.
7. Inclusive to this the EPA recommended assessing the pH of soils for acidity. Acidic soils facilitate the leaching of lead out of the soil into the waterways allowing for bioaccumulation into plant and wild life. Treating acidic soils with phosphates to reach a neutral pH will block the leaching of lead.