{"id":1264,"date":"2026-08-06T14:34:54","date_gmt":"2026-08-06T14:34:54","guid":{"rendered":"https:\/\/blogs.dickinson.edu\/allarm\/?p=1264"},"modified":"2026-08-06T14:34:54","modified_gmt":"2026-08-06T14:34:54","slug":"a-ph-experiment-the-effect-of-light-on-color","status":"publish","type":"post","link":"https:\/\/blogs.dickinson.edu\/allarm\/a-ph-experiment-the-effect-of-light-on-color\/","title":{"rendered":"A pH Experiment: The Effect of Light on Color"},"content":{"rendered":"

pH stands for \u201cPotential of Hydrogen\u201d which\u00a0measures\u00a0how acidic or alkaline\u00a0a substance is.\u00a0pH is\u00a0an important indicator of stream health.\u00a0At ALLARM, the LaMotte\u00a0Precision pH Test Kit is used to measure the hydrogen ion\u00a0concentration\u00a0(pH) in water.\u00a0<\/span>The more hydrogen ions that are present, the more acidic is the solution<\/span>\u200b<\/span>\u00a0(Wood Hole Oceanographic Institution n.d.)<\/span>\u200b<\/span><\/span>.\u00a0pH affects most\u00a0chemical\u00a0and biological\u00a0processes\u00a0in water<\/span>\u200b<\/span>\u00a0(U.S. Environmental Protection Agency (EPA) 2026)<\/span>\u200b<\/span><\/span>.<\/span>\u00a0It is one of the most\u00a0important environmental factors limiting species distributions in aquatic habitats<\/span>\u200b<\/span>\u00a0(U.S. Environmental Protection Agency (EPA) 2026)<\/span>\u200b<\/span><\/span>. pH has a scale from 0 (more acidic) to 14 (very basic). The normal pH of stream water is between 6.5 to 8.5, which is ideal for the survival of aquatic life, including fish reproduction and aquatic insect life. However, if pH becomes too low or too high, it can have harmful biological effects on stream health and biodiversity. For example, both low and high pH levels can reduce the number of species, decrease growth, and lower reproduction rates.<\/span><\/p>\n

Using the\u00a0LaMotte kit\u00a0and the\u00a0Octa-Slide 2 comparator\u00a0(Figure 1),\u00a0we can\u00a0determine\u00a0pH levels.\u00a0LaMotte Precision\u00a0pH\u00a0kit is an easy and accessible\u00a0method\u00a0for\u00a0testing\u00a0pH levels.\u00a0However,\u00a0because\u00a0it\u00a0uses a\u00a0color scale,\u00a0it\u00a0can be\u00a0difficult to\u00a0determine\u00a0an\u00a0accurate\u00a0result.\u00a0This is\u00a0because\u00a0different people\u00a0may perceive\u00a0colors\u00a0differently, which\u00a0can\u00a0make it\u00a0harder\u00a0to\u00a0obtain\u00a0an\u00a0error-free\u00a0measurement.\u00a0In addition,\u00a0the color of\u00a0the test\u00a0result and\u00a0the\u00a0slide color\u00a0can appear different under various lighting conditions, making\u00a0accurate\u00a0reading more difficult.\u00a0There\u00a0are also\u00a0many\u00a0other different methods for pH testing, such\u00a0as\u00a0pH-indicator strips and the Hach Pocket Pro\u00a0+ tester.<\/span><\/p>\n

\"\"

Figure 1: LaMotte pH test kit with Octa-slide color comparator, Octa-bar and reagent bottle.<\/p><\/div>\n

This experiment was designed to show how different\u00a0<\/span>lighting<\/span>\u00a0<\/span>environments<\/span>\u00a0can affect our\u00a0<\/span>results<\/span>\u00a0and\u00a0<\/span>to\u00a0<\/span>identify<\/span>\u00a0<\/span>th<\/span>e best<\/span>\u00a0lighting conditions for this experiment, producing results that are as close to\u00a0<\/span>accurate<\/span>\u00a0as possible<\/span>.\u00a0<\/span>\u00a0<\/span><\/span>\u00a0<\/span><\/p>\n

Method<\/span>s<\/span><\/span><\/strong><\/p>\n

\"\"

Figure 2: Different light environments used in this experiment. The right side of this figure shows indoor light sources, and the left side shows outdoor light sources.<\/p><\/div>\n

\"\"

Table 1: pH standards used in this experiment.<\/p><\/div>\n

Before performing\u00a0the experiment, I\u00a0tested\u00a0each standard to verify\u00a0the\u00a0values\u00a0of\u00a0the pH standards, using\u00a0a\u00a0Fisherbrand\u00a0Accumet\u00a0XL200, a high precision instrument.\u00a0I used\u00a0the\u00a0LaMotte\u00a0Precision pH kit for this experiment\u00a0(Figure 1).\u00a0This is the kit\u00a0we use at\u00a0ALLARM,\u00a0and our volunteers use this for monitoring\u00a0stream\u00a0pH.\u00a0Three different pH concentration standards\u00a0were used\u00a0to compare the measured values\u00a0with the\u00a0actual value, 6,\u00a08, and 9\u00a0(Table\u00a01).\u00a0Five ALLARM members,\u00a0including\u00a0full-time\u00a0staff members and\u00a0student watershed\u00a0coordinators,\u00a0participated\u00a0in the\u00a0experiment. I\u00a0conducted\u00a0the experiment at\u00a0the\u00a0ALLARM office\u00a0on\u00a0the same\u00a0day\u00a0at\u00a0and at\u00a0the same time\u00a0for each light\u00a0source.\u00a0<\/span>\u00a0<\/span><\/p>\n

After collecting data\u00a0for this experiment,\u00a0I recorded\u00a0it in\u00a0an\u00a0Excel\u00a0Spreadsheet. I organized\u00a0the data\u00a0into\u00a0five\u00a0categorized datasets\u00a0based on the specific lighting conditions\u00a0to enable\u00a0better comparisons\u00a0and\u00a0ensure\u00a0accurate\u00a0results.\u00a0In each dataset, the perceived pH\u00a0values (for pH 6, pH\u00a08,\u00a0and\u00a0pH 9) are tracked\u00a0individually\u00a0for\u00a0each\u00a0participant\u00a0to clearly show how different light resources affect color perception.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><\/p>\n

Results<\/span><\/span><\/strong><\/p>\n

\"\"

Table 2: This table shows the percent error (%) for three different concentration standards across different environments. The red color on this table indicates the highest error, and the green color indicates the lowest error or zero.<\/p><\/div>\n

In\u00a0<\/span>T<\/span>able<\/span>\u00a0<\/span>2<\/span>,\u00a0<\/span>the highest\u00a0<\/span>error\u00a0<\/span>is\u00a0<\/span>7.50%<\/span>\u00a0<\/span>at<\/span>\u00a0pH 6 in\u00a0<\/span>the\u00a0<\/span>sunlight\u00a0<\/span>light source<\/span>.<\/span>\u00a0<\/span>The lowest error is<\/span>\u00a0<\/span>0.00%. This was case for\u00a0<\/span>pH 6<\/span>\u00a0on<\/span>\u00a0white paper, pH\u00a0<\/span>8 in the shade of a tree<\/span>,\u00a0<\/span>pH 9 in white paper and<\/span>\u00a0in<\/span>\u00a0<\/span>sunlight,<\/span>\u00a0<\/span>and\u00a0<\/span>for pH 9 in lab light<\/span>.<\/span>\u00a0<\/span>Therefore,<\/span>\u00a0<\/span>as shown in Table\u00a0<\/span>2<\/span>,<\/span>\u00a0lower\u00a0<\/span>conce<\/span>n<\/span>tration<\/span>\u00a0<\/span>(such<\/span>\u00a0as the\u00a0<\/span>pH 6<\/span>\u00a0standard<\/span>)<\/span>\u00a0<\/span>produce<\/span>d<\/span>\u00a0highe<\/span>r<\/span>\u00a0error<\/span>s, while<\/span>\u00a0pH 9 had\u00a0<\/span>lowest<\/span>\u00a0<\/span>error\u00a0<\/span>overall.<\/span>\u00a0<\/span><\/span>\u00a0<\/span><\/p>\n

\"\"

Figure 3: Results for pH 6, 8, and 9 in the shade of a tree.<\/p><\/div>\n

Looking at\u00a0<\/span>F<\/span>igure 2<\/span>\u00a0and\u00a0<\/span>the\u00a0<\/span>results\u00a0<\/span>in<\/span>\u00a0<\/span>T<\/span>able<\/span>\u00a0<\/span>2<\/span>, we<\/span>\u00a0can\u00a0<\/span>analyze<\/span>\u00a0that the\u00a0<\/span>shaded<\/span>\u00a0tree<\/span>\u00a0<\/span>produced<\/span>\u00a0the lowest percentage of error\u00a0<\/span>for all<\/span>\u00a0standards. In addition,<\/span>\u00a0pH 9<\/span>\u00a0was read correctly\u00a0<\/span>by 4 out of 5 participants<\/span>.<\/span><\/p>\n

\"\"

Figure 4: Results from direct to sunlight for the pH 6, 8, and 9 concentration standards.<\/p><\/div>\n

From Figure\u00a0<\/span>4 and Table 3<\/span>,<\/span>\u00a0t<\/span>he highest error\u00a0<\/span>was<\/span>\u00a0caused<\/span>\u00a0by<\/span>\u00a0direct\u00a0<\/span>exposure<\/span>\u00a0<\/span>to sunlight<\/span>.<\/span>\u00a0Th<\/span>is light sour<\/span>ce made the results<\/span>\u00a0<\/span>differ<\/span>\u00a0significantly from<\/span>\u00a0the ac<\/span>tual\u00a0<\/span>value<\/span>s, e<\/span>specially<\/span>\u00a0the results\u00a0<\/span>at a\u00a0<\/span>pH\u00a0<\/span>of\u00a0<\/span>6 concentration<\/span>.\u00a0<\/span>However,\u00a0<\/span>at<\/span>\u00a0pH 9<\/span>,<\/span>\u00a0all participants read the values correctly<\/span>.\u00a0<\/span>\u00a0<\/span><\/p>\n

\"\"

Figure 5: Results from direct to lab light for the pH 6, 8, and 9 concentration standards.<\/p><\/div>\n

The\u00a0<\/span>artificial<\/span>\u00a0light (lab light)<\/span>\u00a0caused less error for<\/span>\u00a0<\/span>the<\/span>\u00a0<\/span>pH\u00a0<\/span>6 concentration\u00a0<\/span>compare<\/span>d<\/span>\u00a0to\u00a0<\/span>the\u00a0<\/span>other light source<\/span>;<\/span>\u00a0it was<\/span>\u00a0read correctly by 4 out of 5 participants<\/span>.<\/span>\u00a0<\/span>The l<\/span>ab light was also\u00a0<\/span>a<\/span>\u00a0<\/span>good light source for<\/span>\u00a0<\/span>the\u00a0<\/span>pH 9 concentration<\/span>\u00a0because it produced the same results for everyone.\u00a0<\/span><\/span>\u00a0<\/span><\/p>\n

\"\"

Figure 6: Results from on white background (white paper) for the pH 6, 8, and 9 concentration standards.<\/p><\/div>\n

\"\"

Figure 7: Results from in front of a window for the pH 6, 8, and 9 concentration standards.<\/p><\/div>\n

For each\u00a0<\/span>standard<\/span>\u00a0<\/span>tested\u00a0<\/span>in different<\/span>\u00a0environments,<\/span>\u00a0<\/span>the results<\/span>\u00a0<\/span>differed from\u00a0<\/span>the\u00a0<\/span>actual<\/span>\u00a0values<\/span>\u2014especially<\/span>\u00a0for\u00a0<\/span>pH<\/span>\u00a06 and\u00a0<\/span>8<\/span>. However,<\/span>\u00a0for pH 9<\/span>,<\/span>\u00a0<\/span>the\u00a0<\/span>result<\/span>\u00a0w<\/span>ere\u00a0<\/span>almost\u00a0<\/span>the<\/span>\u00a0<\/span>same<\/span>\u00a0for<\/span>\u00a0every light source<\/span>\u00a0<\/span>expect<\/span>\u00a0for the window light<\/span>.\u00a0<\/span><\/span>\u00a0<\/span><\/p>\n

Discussion\u00a0<\/strong><\/p>\n

The data from the results\u00a0shows\u00a0that,\u00a0for each pH standard,\u00a0we\u00a0used\u00a0different environment light sources\u00a0that\u00a0were\u00a0helpful. However,\u00a0there is not one light source that provides\u00a0clear reading for all standards for all participants.\u00a0<\/span>\u00a0<\/span><\/p>\n

Overall,\u00a0for high pH concentration standards,\u00a0such as\u00a0pH\u00a09,\u00a0the\u00a0best\u00a0light source\u00a0was\u00a0shade of a\u00a0tree,\u00a0and this source produced the\u00a0most\u00a0accurate\u00a0results.\u00a0For\u00a0the lower\u00a0standards,\u00a0such as pH 6,\u00a0artificial light or indoor\u00a0lighting produced\u00a0the\u00a0most\u00a0accurate\u00a0results.\u00a0However,\u00a0according to our data,\u00a0pH 6\u00a0still\u00a0had\u00a0more\u00a0inaccurate results compared with the\u00a0other standards.\u00a0<\/span>\u00a0<\/span><\/p>\n

\"\"

Figure 8: Octa-slide without black case.<\/p><\/div>\n

From\u00a0the\u00a0Table\u00a03, we can see\u00a0that\u00a0the most\u00a0accurate\u00a0results were\u00a0obtained\u00a0for\u00a0high\u00a0pH\u00a0standard\u00a0(such as pH\u00a09) in every different environment. This suggests that\u00a0results are\u00a0easier to\u00a0distinguish\u00a0in\u00a0the presence of higher pH standards. However, for low pH standards\u00a0(such as pH\u00a06)\u00a0it\u2019s\u00a0difficult to\u00a0distinguish. In contrast, low pH standards (such as pH 6) are more difficult to distinguish\u00a0accurately.\u00a0<\/span>\u00a0<\/span><\/p>\n

This experiment was\u00a0conducted\u00a0on\u00a0two different days under\u00a0the\u00a0same weather conditions. One\u00a0factor to\u00a0keep\u00a0in mind\u00a0is\u00a0that cloudy\u00a0weather\u00a0can also affect\u00a0the\u00a0data\u00a0results.\u00a0If the\u00a0experiment\u00a0is performed\u00a0outdoor\u00a0on a cloudy day, there may be less available light, which\u00a0increase\u00a0error because enough light\u00a0may not reach the\u00a0sample.\u00a0Although\u00a0the\u00a0results\u00a0in Table 3,\u00a0indicates\u00a0that the shade of a tree is a better light source,\u00a0the shade conditions were only applicable for sunny days; on cloudy days, the shaded area would\u00a0likely be\u00a0darker and may not\u00a0provide sufficient light.\u00a0Finally,\u00a0because pH becomes time-sensitive once pH indicator is added, it is\u00a0not\u00a0good to wait for a sunny day, and it is\u00a0best to\u00a0perform the experiment\u00a0indoor\u00a0with sufficient lighting, such as direct artificial light\u00a0(Figure\u00a02).\u00a0<\/span><\/p>\n

\"\"

Figure 9: This figure shows Octa-slide without their black case held next to the sample on the right, and one sample held over an Octa-slide on the left.<\/p><\/div>\n

One other suggestion we can give\u00a0is to\u00a0hold your\u00a0sample\u00a0over\u00a0the\u00a0Octa-slide or next to each other without\u00a0using the black case (figure\u00a09). This\u00a0makes it\u00a0easier\u00a0to read the results\u00a0because more light will\u00a0reach\u00a0the\u00a0sample.\u00a0Sometimes reading with\u00a0the\u00a0black case will block the light and the color scale, which makes it difficult\u00a0to read. Also, without the black case, we can put our sample near each\u00a0color scale, which makes it easier to compare.\u00a0<\/span>\u00a0<\/span><\/p>\n

One important fact about this experiment is that one\u00a0of our\u00a0participants\u00a0is\u00a0red-green\u00a0color blind.\u00a0Therefore,\u00a0we tested whether\u00a0the Precision\u00a0pH kit\u00a0method is color-blind friendly. However,\u00a0according to\u00a0the results\u00a0and\u00a0participant\u2019s\u00a0comments,\u00a0it was difficult for\u00a0them\u00a0to\u00a0read the results and\u00a0about\u00a0half of\u00a0their\u00a0readings\u00a0involved\u00a0guessing.\u00a0We\u00a0therefore\u00a0suggest that the kit is\u00a0not\u00a0red-green\u00a0color-blind friendly.\u00a0<\/span>\u00a0<\/span><\/p>\n

In conclusion, this experiment was\u00a0designed to\u00a0determine\u00a0the\u00a0best light source for\u00a0accurately reading\u00a0pH\u00a0standards.\u00a0According to our results, we can suggest that the most error-prone light source is in the shade of a tree\u00a0on sunny days.\u00a0The experiment was\u00a0helpful in showing human error and how each person perceives color in different environments. Finally, we can minimize our error by being more careful and it is also best to have\u00a0more people take readings as a second check to achieve more\u00a0accurate\u00a0results.\u00a0<\/span><\/p>\n

References<\/strong><\/p>\n

1. <\/span>“The pH Scale,” Woods Hole Oceanographic Institution, accessed Ju<\/span>ne<\/span>2<\/span>0<\/span>, 2026,\u00a0<\/span><\/span>https:\/\/www.whoi.edu\/ocean-learning-hub\/ocean-topics\/how-the-ocean-works\/ocean-chemistry\/ocean-acidification\/the-ph-scale\/<\/span><\/span><\/a>.<\/span><\/span>\u00a0<\/span><\/p>\n

2. US Environmental Protection Agency. \u201c<\/span>pH.<\/span>\u201d Causal Analysis\/Diagnosis Decision Information System (CADDIS). Accessed Ju<\/span>ne<\/span>\u00a02<\/span>0<\/span>, 2026.\u00a0<\/span><\/span>https:\/\/www.epa.gov\/caddis\/ph<\/span><\/span><\/a>.<\/span><\/span>\u00a0<\/span><\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

pH stands for \u201cPotential of Hydrogen\u201d which\u00a0measures\u00a0how acidic or alkaline\u00a0a substance is.\u00a0pH is\u00a0an important indicator of stream health.\u00a0At ALLARM, the LaMotte\u00a0Precision pH Test Kit is used to measure the hydrogen ion\u00a0concentration\u00a0(pH) in water.\u00a0The more hydrogen ions that are present, the more acidic is the solution\u200b\u00a0(Wood Hole Oceanographic Institution n.d.)\u200b.\u00a0pH affects most\u00a0chemical\u00a0and biological\u00a0processes\u00a0in water\u200b\u00a0(U.S. Environmental Protection […]<\/p>\n","protected":false},"author":5797,"featured_media":1265,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1264","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized"],"acf":[],"_links":{"self":[{"href":"https:\/\/blogs.dickinson.edu\/allarm\/wp-json\/wp\/v2\/posts\/1264","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.dickinson.edu\/allarm\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.dickinson.edu\/allarm\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.dickinson.edu\/allarm\/wp-json\/wp\/v2\/users\/5797"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.dickinson.edu\/allarm\/wp-json\/wp\/v2\/comments?post=1264"}],"version-history":[{"count":5,"href":"https:\/\/blogs.dickinson.edu\/allarm\/wp-json\/wp\/v2\/posts\/1264\/revisions"}],"predecessor-version":[{"id":1284,"href":"https:\/\/blogs.dickinson.edu\/allarm\/wp-json\/wp\/v2\/posts\/1264\/revisions\/1284"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.dickinson.edu\/allarm\/wp-json\/wp\/v2\/media\/1265"}],"wp:attachment":[{"href":"https:\/\/blogs.dickinson.edu\/allarm\/wp-json\/wp\/v2\/media?parent=1264"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.dickinson.edu\/allarm\/wp-json\/wp\/v2\/categories?post=1264"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.dickinson.edu\/allarm\/wp-json\/wp\/v2\/tags?post=1264"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}