# set pH flash

This function calculates the equilibrium solution at a specified pH by varying inflows of acid and/or base titrant(s).

## set pH

<mark style="color:green;">`POST`</mark> `https://api.olisystems.com/engine/flash/{dbs_file_id}/setph`

fix the pH of the aqueous phase by varying acid/base amount

#### Headers

| Name          | Type   | Description            |
| ------------- | ------ | ---------------------- |
| Authorization | string | Bearer {access\_token} |
| Content-Type  | string | application/json       |

{% tabs %}
{% tab title="200 Please look at "API call blueprint" page on how to obtain results" %}

```
{
	"code": 200,
	"data": {
		"file_id": "dee854a6-59db-487d-ad08-a20dee691133",
		"jobId": "f6b3375e-cd0f-4ace-a5ee-71e047b76754",
		"resultsLink": "https://devapi.olisystems.com/result/flash/f6b3375e-cd0f-4ace-a5ee-71e047b76754?context=engine",
		"status": "IN PROGRESS"
	},
	"message": "Process execution started Successfully",
	"status": "SUCCESS"
}
```

{% endtab %}
{% endtabs %}

### Request payload

```javascript
{
    "params": {
        "temperature": {
            "value": 30.0,
            "unit": "°C"
        },
        "pressure": {
            "value": 1.5,
            "unit": "atm"
        },
        "targetPH": {
            "value": 8.0,
            "unit": ""
        },
        "pHAcidTitrant": "HCL",
        "pHBaseTitrant": "NAOH",
        "inflows": {
            "unit": "mol",
            "values": {
                "H2O": 50.0,
                "CO2": 10.0,
                "NACL": 20.0,
                "BENZENE": 10.0,
                "HCL": 0.0,
                "NAOH": 0.0
            }
        }
    }
}
```

| **params**    | type                                                           | description                                                                                       |
| ------------- | -------------------------------------------------------------- | ------------------------------------------------------------------------------------------------- |
| temperature   | [valueObject](https://devdocs.olisystems.com/terms-definition) | specified or initial guess temperature with [unit](https://devdocs.olisystems.com/input-unit-set) |
| pressure      | [valueObject](https://devdocs.olisystems.com/terms-definition) | specified or initial guess pressure with [unit](https://devdocs.olisystems.com/input-unit-set)    |
| targetPH      | value                                                          | specified target pH of the solution                                                               |
| pHAcidTitrant | string                                                         | inflow species name for pH acid titrant                                                           |
| pHBaseTitrant | string                                                         | inflow species name for pH base titrant                                                           |

{% hint style="danger" %}
One or both of **params.pHAcidTitrant** and **params.pHBaseTitrant** need to be specified. If only one titrant is to be specified, it is the same to specify it as **params.pHAcidTitrant** or **params.pHBaseTitrant** regardless of the chemical nature of the solvent.
{% endhint %}

{% hint style="info" %}
in addition to the inputs shown above some optional properties may also be specified. They can be viewed [here](https://devdocs.olisystems.com/optional-inputs)
{% endhint %}

### Response (status = PROCESSED)

```javascript
{
    "code": 200,
    "data": {
        "result": {
            "addedTitrants": [
                {
                    "name": "NAOH",
                    "titrantType": "Base",
                    "unit": "mol",
                    "value": 9.998955177015539
                }
            ],
            ...<snip>...
        }
    }, 
    "message": "Results returned successfully", 
    "status": "PROCESSED"
}
```

The output of this calculation is the [**stream output** ](https://devdocs.olisystems.com/stream-output-json)which is common result output for all OLI's flash calculations or an [**error**](https://devdocs.olisystems.com/error-output)**.** In addition to this output the result also contains the amounts of added titrants and can be conveniently retrieved from the **data.result.addedTitrants** array&#x20;

| data.result.addedTitrants [\[ { } \]](https://devdocs.olisystems.com/terms-definition) | type   | description                                                                                       |
| -------------------------------------------------------------------------------------- | ------ | ------------------------------------------------------------------------------------------------- |
| titrantType                                                                            | string | titrant type, i.e. "Acid" or "Base". This field will be missing if only one titrant is specified. |
| name                                                                                   | string | inflow name of the titrant                                                                        |
| value                                                                                  | number | added titrant amount                                                                              |
| unit                                                                                   | string | unit of added titrant amount                                                                      |

### Survey Calculation

Survey calculation is supported for the variables below. Please refer to [Survey calculation](https://devdocs.olisystems.com/survey-calculation) for explained input schema.

| supported **params.surveyInputs\[{}].field** |
| -------------------------------------------- |
| "/params/temperature/value"                  |
| "/params/pressure/value"                     |
| "/params/targetPH/value"                     |


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://devdocs.olisystems.com/group1/api-functions/setph.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.