Editor comments for Miñambres et al. (2014) The effect of low solubility organic acids on the hygroscopicity of sodium halide aerosols, submitted to ACP

General comments:
The manuscript has improved during the peer-review process. However, there is still some improvement that is needed in terms of scientific quality that needs to be addressed before the manuscript can be accepted. The scientific conclusions from the data are quite strongly presented. The data is not contradicting these conclusions, but a more detailed analysis on the quality of the data should be presented or the statements should be revised / softened.

Error analysis: 4-9 degrees are assumed to be the error in temperatures (6.5 degrees in the other reply), but none are stated for relative humidity. In particularly in the deliquescence and efflorescence analysis, RH needs to be well quantified to produce comparable data with other methods and studies. The agreement of the data with theoretical value for NaCl DRH gives confidence on the method, but this needs to be mentioned in the text together with associated errors and their effects on the results.

Section 3.4.3 discusses various processes affecting deliquescence and efflorescence. Please underline more clearly, how your results add to this knowledge. Please quantify the effects, when possible.

Section 3.5: The beginning could form a short sub-section in the methods section as it helps the reader to understand, how the spectra changes in different RHs.

There seems to be some mistakes with Figure numbering, which needs to be fixed. I list other relevant minor as well as technical comments that should be implemented below.

A list of technical and minor comments:
line 58: … mass transfer of gaseous compounds …
line 97: … proportions that may …
line 104: … the organic mass indicating that …
line 112: New paragraph after Ault et al. 2013.
line 132: process of cloud condensation nuclei formation and aerosol growth to climatically relevant sizes.
line 139: … fundamental properties of of marine aerosol particles…
line 141: IPCC 2013
line 148: … efflorescence of the particles at Efflorescence relative humidity (ERH)…
line 153: … aerosol modeling that …
line 171: What is the relevance of these sources (seed oil, cooking, emission from plants) for marine aerosols? What are sources in marine environment?
line 176: … long chain acids that may
line 183-198: Please move the whole paragraph to the beginning of section 2. It gives a good overview of the potential of the method that you use.
line 190: … Veghte et al. 2013). A few …
line 213: … 1 cm internal diameter)
line 207: How well is RH controlled? How stable the system is? How is RH measured?
line 220: … T1 was varied from…
line 221: Higher temperature indicates higher concentration in the gas phase leading to enhanced condensation and larger particles and therefore thicker coating.
line 232: … ambient temperature that effectively …
line 243: … from a collimated …
line 255-256: … intensity of 10-10 A with a working…
line 264: … isolated without a tendency …
line 291: … spectra of pure, homogeneously nucleated…
line 293: … were assumed to be composed of pure carboxylic acids.
line 309: … octanoic acid that is absent…
line 310: The last sentence in the paragraph needs a reference or a stronger support from the data.
line 314: … significant, as they can be related to surface effects …
line 324: Figure 3?
Line 325: … higher than those of homogeneous …
line 326: For NaX/HA particles, bands caused both by gaseous and condensed phase HA …
line 329: The observed carbonyl…
line 332: For all acids the C=0 …
line 334: … that of the homogeneously …
line 335: … of C=0 is around 70 …
line 336: … stretch originating from …
line 340: … hygroscopic properties will be …
line 348: … or HA due to their …
line 349: … that hinders their manipulation …
line 351: … gold layer. As NaCl is ..
line 354: … a much smaller number of particles …
line 355: … length. This is in accordance with …
line 356: … amorphous and elongated. (or highly elongated?)
line 358: Is the same number of particles verified with the CPC?
line 360: How do you verify thicker coating for the smaller particles?
line 378: In all cases we paid …
line 380: LA/NaX particles the carbonyl …
line 381: … with RH. For NaX/HA particles, on the contrary, the band …
line 382: Figure 5?
line 385 onwards: It is not clear to which figure the text is connected to. Please clarify.
line 389: This paragraph belongs to the beginning of the next section, 3.4.2.
line 391: … systems at RH near saturation, the spectra …
line 405: … each of the inorganic salts as a function of RH with a special attention towards the deliquescence and efflorescence behavior of the mixed particles.
line 408: … pure NaCl particles that …
line 408: define “very similar”.
line 410: Reformulate sentence starting: However, SEM results … At least the word that is not used properly. Roundish is not a good adjective in a scientific literature.
line 414: A word “surfactant” is better than covering.
line 415: … substantially lower than the value corresponding to pure NaCl.
line 416: Quantify the term “slight”.
line 418: New paragraph for the efflorescence discussion. Please provide references to other works that have studied efflorescence of NaCl. Are your results in agreement with them?
line 420: For all acids the particles retain …
line 426: Figure 6?
line 427: What is your error estimate for the stated RH?
line 429: On the other hand, OA and as a surfactant does not have any effect …
line 430: … NaBr. The deliquescence …
line 432: Grow faster? Based on your replies, I understand that your results are in equilibrium.
line 432: … acid surfactant are very …
line 443: surfactant instead of covering.
line 446: However, the HA-covered …
line 449: surfactant retains …
line 455: Figure 6?
line 455: … is dependent on both the properties of inorganic salts and those of the organic acids.
line 456: sentence starting “Whereas …” is difficult to follow, please rephrase.
line 457: NaCl with respect to pure salt.
line 459: … admits water condensation at any RH. (What is the lowest RH? Does this hold for 0 % RH?)
line 459: In efflorescence a coherent behavior is observed for all systems. The presence …
line 466: … tend to orientate their polar groups facing the salt surface so that ..
line 469: Is there a better reference for the polarizabilities than a web-page?
line 477: In that way the differences in …
line 480: … the surface that can be …
line 487: … variation with respect to …
line 489: in some cases? The results indicate a large effect, please quantify this.
line 492: New paragraph starting from: “Although …
line 494: … with NaBr the changes in the …
line 495: … a quite small change in DRH … Please quantify quite small.
line 496: … are considerable indicating strong … Remove parenthesis and please quantify considerable.
line 498: … organic acids. It forms a barrier …
line 501: … enhance condensation of water ..
line 503: … acceptance is not a proper word here.
line 505: … in the efflorescence …
line 509: Please clarify the connection to this work.
line 511: Can it be seen in your data?
line 513: … having low water solubility. In all deliquescence curves in Figure …
line 520: … must be: so there cannot be any other explanation?
line 528: Does there have to be a physical hole? Why cannot water just diffuse through the surfactant (mass transfer effect). Please add references to other similar work to support your statements.
line 566: organic surfactant
line 567: Could there be some evaporation in SEM? How rapidly is gold added to the sample?
line 584: … thickness is much larger than … What is the estimated monolayer thickness? Please specify.

Conclusions and atmospheric implications:
Please use past tense.
line 595: This work studied the …
line 598: … techniques allowed us to detect …
I suggest moving the surfactant thickness related conclusions (from lines 601-605) towards the end of this section. line 601: … deduced from the infrared …
line 606: It was found that …
line 611: Growth factor?
Start a new paragraph from line 615: The general consequence …
line 623: achieved … provided …
line 628: Based on our data, there is no …
line 639: … having a low water solubility …

References:
Please correct capitalization, journal names, consistent journal acronyms, typos etc. in many of the references.

Figure captions:
Figure 1: A diagram of … Explain thermohygrometer. Explain T1, T2
Figure 2: There are three panels, add A), B) and C) accordingly. Please use y-labels in a consistent manner.
Figure 3: Add A), B) and C) for the different panels.
Figure 5 & 6: How accurately can you define RH in these experiments? With three significant figures? Is RH really 100 % in one experiment?
Figure 7: Include an explanatory text indicating that left panel is for deliquescence and right panel for efflorescence. How do you calculate liquid water mass? Please clarify.
Figure 8: In my opinion two dimensional figure with x-axis of RH and y-axis of N_acid/N_water with all the different experiments in different symbols would work better.
Table 1: #C number of carbon atoms
Table 2: Use also HA, OA and LA to be consistent with the text.

Thank you for the revised version.

The work is now accepted for publication with technical corrections.


I found few technical issues that I list below.


line 651-654:
Please add a reference after the statement:
This is in accordance with former studies of sodium halides with succinic acid, which showed a salt-specific behavior.

Correct punctuation for better reading:
Consequently, although it is customary to extrapolate the water uptake behavior of NaCl particles to sea salt aerosol due to the predominance of this species in marine salt, the detailed picture can be more complex.

line 200:
Correct reference error.

line 174:
Condensation is the proper term here?
The substances emitted in coastal areas can condense onto preexisting marine aerosol andmodify their properties. HA, OA and…